| Age | Commit message (Collapse) | Author |
|---|
|
Use x86_vfm (vendor, family, module) to detect CPUs that are affected by
PERF_GLOBAL_CTRL bugs instead of manually checking the family and model.
The new VFM infrastructure encodes all information in one handy location.
No functional change intended.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20240520224620.9480-10-tony.luck@intel.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Move shadow_phys_bits into "struct kvm_host_values", i.e. into KVM's
global "kvm_host" variable, so that it is automatically exported for use
in vendor modules. Rename the variable/field to maxphyaddr to more
clearly capture what value it holds, now that it's used outside of the
MMU (and because the "shadow" part is more than a bit misleading as the
variable is not at all unique to shadow paging).
Recomputing the raw/true host.MAXPHYADDR on every use can be subtly
expensive, e.g. it will incur a VM-Exit on the CPUID if KVM is running as
a nested hypervisor. Vendor code already has access to the information,
e.g. by directly doing CPUID or by invoking kvm_get_shadow_phys_bits(), so
there's no tangible benefit to making it MMU-only.
Link: https://lore.kernel.org/r/20240423221521.2923759-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Add "struct kvm_host_values kvm_host" to hold the various host values
that KVM snapshots during initialization. Bundling the host values into
a single struct simplifies adding new MSRs and other features with host
state/values that KVM cares about, and provides a one-stop shop. E.g.
adding a new value requires one line, whereas tracking each value
individual often requires three: declaration, definition, and export.
No functional change intended.
Link: https://lore.kernel.org/r/20240423221521.2923759-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Print the SPTEs that correspond to the faulting GPA on an unexpected EPT
Violation #VE to help the user debug failures, e.g. to pinpoint which SPTE
didn't have SUPPRESS_VE set.
Opportunistically assert that the underlying exit reason was indeed an EPT
Violation, as the CPU has *really* gone off the rails if a #VE occurs due
to a completely unexpected exit reason.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Dump the VMCS on an unexpected #VE, otherwise it's practically impossible
to figure out why the #VE occurred.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Always handle #VEs, e.g. due to prove EPT Violation #VE failures, in L0,
as KVM does not expose any #VE capabilities to L1, i.e. any and all #VEs
are KVM's responsibility.
Fixes: 8131cf5b4fd8 ("KVM: VMX: Introduce test mode related to EPT violation VE")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Point vmcs02.VE_INFORMATION_ADDRESS at the vCPU's #VE info page when
initializing vmcs02, otherwise KVM will run L2 with EPT Violation #VE
enabled and a VE info address pointing at pfn 0.
Fixes: 8131cf5b4fd8 ("KVM: VMX: Introduce test mode related to EPT violation VE")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Don't terminate the VM on an unexpected #VE, as it's extremely unlikely
the #VE is fatal to the guest, and even less likely that it presents a
danger to the host. Simply resume the guest on "failure", as the #VE info
page's BUSY field will prevent converting any more EPT Violations to #VEs
for the vCPU (at least, that's what the BUSY field is supposed to do).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Pull KVM updates from Paolo Bonzini:
"ARM:
- Move a lot of state that was previously stored on a per vcpu basis
into a per-CPU area, because it is only pertinent to the host while
the vcpu is loaded. This results in better state tracking, and a
smaller vcpu structure.
- Add full handling of the ERET/ERETAA/ERETAB instructions in nested
virtualisation. The last two instructions also require emulating
part of the pointer authentication extension. As a result, the trap
handling of pointer authentication has been greatly simplified.
- Turn the global (and not very scalable) LPI translation cache into
a per-ITS, scalable cache, making non directly injected LPIs much
cheaper to make visible to the vcpu.
- A batch of pKVM patches, mostly fixes and cleanups, as the
upstreaming process seems to be resuming. Fingers crossed!
- Allocate PPIs and SGIs outside of the vcpu structure, allowing for
smaller EL2 mapping and some flexibility in implementing more or
less than 32 private IRQs.
- Purge stale mpidr_data if a vcpu is created after the MPIDR map has
been created.
- Preserve vcpu-specific ID registers across a vcpu reset.
- Various minor cleanups and improvements.
LoongArch:
- Add ParaVirt IPI support
- Add software breakpoint support
- Add mmio trace events support
RISC-V:
- Support guest breakpoints using ebreak
- Introduce per-VCPU mp_state_lock and reset_cntx_lock
- Virtualize SBI PMU snapshot and counter overflow interrupts
- New selftests for SBI PMU and Guest ebreak
- Some preparatory work for both TDX and SNP page fault handling.
This also cleans up the page fault path, so that the priorities of
various kinds of fauls (private page, no memory, write to read-only
slot, etc.) are easier to follow.
x86:
- Minimize amount of time that shadow PTEs remain in the special
REMOVED_SPTE state.
This is a state where the mmu_lock is held for reading but
concurrent accesses to the PTE have to spin; shortening its use
allows other vCPUs to repopulate the zapped region while the zapper
finishes tearing down the old, defunct page tables.
- Advertise the max mappable GPA in the "guest MAXPHYADDR" CPUID
field, which is defined by hardware but left for software use.
This lets KVM communicate its inability to map GPAs that set bits
51:48 on hosts without 5-level nested page tables. Guest firmware
is expected to use the information when mapping BARs; this avoids
that they end up at a legal, but unmappable, GPA.
- Fixed a bug where KVM would not reject accesses to MSR that aren't
supposed to exist given the vCPU model and/or KVM configuration.
- As usual, a bunch of code cleanups.
x86 (AMD):
- Implement a new and improved API to initialize SEV and SEV-ES VMs,
which will also be extendable to SEV-SNP.
The new API specifies the desired encryption in KVM_CREATE_VM and
then separately initializes the VM. The new API also allows
customizing the desired set of VMSA features; the features affect
the measurement of the VM's initial state, and therefore enabling
them cannot be done tout court by the hypervisor.
While at it, the new API includes two bugfixes that couldn't be
applied to the old one without a flag day in userspace or without
affecting the initial measurement. When a SEV-ES VM is created with
the new VM type, KVM_GET_REGS/KVM_SET_REGS and friends are rejected
once the VMSA has been encrypted. Also, the FPU and AVX state will
be synchronized and encrypted too.
- Support for GHCB version 2 as applicable to SEV-ES guests.
This, once more, is only accessible when using the new
KVM_SEV_INIT2 flow for initialization of SEV-ES VMs.
x86 (Intel):
- An initial bunch of prerequisite patches for Intel TDX were merged.
They generally don't do anything interesting. The only somewhat
user visible change is a new debugging mode that checks that KVM's
MMU never triggers a #VE virtualization exception in the guest.
- Clear vmcs.EXIT_QUALIFICATION when synthesizing an EPT Misconfig
VM-Exit to L1, as per the SDM.
Generic:
- Use vfree() instead of kvfree() for allocations that always use
vcalloc() or __vcalloc().
- Remove .change_pte() MMU notifier - the changes to non-KVM code are
small and Andrew Morton asked that I also take those through the
KVM tree.
The callback was only ever implemented by KVM (which was also the
original user of MMU notifiers) but it had been nonfunctional ever
since calls to set_pte_at_notify were wrapped with
invalidate_range_start and invalidate_range_end... in 2012.
Selftests:
- Enhance the demand paging test to allow for better reporting and
stressing of UFFD performance.
- Convert the steal time test to generate TAP-friendly output.
- Fix a flaky false positive in the xen_shinfo_test due to comparing
elapsed time across two different clock domains.
- Skip the MONITOR/MWAIT test if the host doesn't actually support
MWAIT.
- Avoid unnecessary use of "sudo" in the NX hugepage test wrapper
shell script, to play nice with running in a minimal userspace
environment.
- Allow skipping the RSEQ test's sanity check that the vCPU was able
to complete a reasonable number of KVM_RUNs, as the assert can fail
on a completely valid setup.
If the test is run on a large-ish system that is otherwise idle,
and the test isn't affined to a low-ish number of CPUs, the vCPU
task can be repeatedly migrated to CPUs that are in deep sleep
states, which results in the vCPU having very little net runtime
before the next migration due to high wakeup latencies.
- Define _GNU_SOURCE for all selftests to fix a warning that was
introduced by a change to kselftest_harness.h late in the 6.9
cycle, and because forcing every test to #define _GNU_SOURCE is
painful.
- Provide a global pseudo-RNG instance for all tests, so that library
code can generate random, but determinstic numbers.
- Use the global pRNG to randomly force emulation of select writes
from guest code on x86, e.g. to help validate KVM's emulation of
locked accesses.
- Allocate and initialize x86's GDT, IDT, TSS, segments, and default
exception handlers at VM creation, instead of forcing tests to
manually trigger the related setup.
Documentation:
- Fix a goof in the KVM_CREATE_GUEST_MEMFD documentation"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (225 commits)
selftests/kvm: remove dead file
KVM: selftests: arm64: Test vCPU-scoped feature ID registers
KVM: selftests: arm64: Test that feature ID regs survive a reset
KVM: selftests: arm64: Store expected register value in set_id_regs
KVM: selftests: arm64: Rename helper in set_id_regs to imply VM scope
KVM: arm64: Only reset vCPU-scoped feature ID regs once
KVM: arm64: Reset VM feature ID regs from kvm_reset_sys_regs()
KVM: arm64: Rename is_id_reg() to imply VM scope
KVM: arm64: Destroy mpidr_data for 'late' vCPU creation
KVM: arm64: Use hVHE in pKVM by default on CPUs with VHE support
KVM: arm64: Fix hvhe/nvhe early alias parsing
KVM: SEV: Allow per-guest configuration of GHCB protocol version
KVM: SEV: Add GHCB handling for termination requests
KVM: SEV: Add GHCB handling for Hypervisor Feature Support requests
KVM: SEV: Add support to handle AP reset MSR protocol
KVM: x86: Explicitly zero kvm_caps during vendor module load
KVM: x86: Fully re-initialize supported_mce_cap on vendor module load
KVM: x86: Fully re-initialize supported_vm_types on vendor module load
KVM: x86/mmu: Sanity check that __kvm_faultin_pfn() doesn't create noslot pfns
KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values
...
|
|
KVM VMX changes for 6.10:
- Clear vmcs.EXIT_QUALIFICATION when synthesizing an EPT Misconfig VM-Exit to
L1, as per the SDM.
- Move kvm_vcpu_arch's exit_qualification into x86_exception, as the field is
used only when synthesizing nested EPT violation, i.e. it's not the vCPU's
"real" exit_qualification, which is tracked elsewhere.
- Add a sanity check to assert that EPT Violations are the only sources of
nested PML Full VM-Exits.
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD
LoongArch KVM changes for v6.10
1. Add ParaVirt IPI support.
2. Add software breakpoint support.
3. Add mmio trace events support.
|
|
Mixture of bitfields and types is weird and really not intuitive, remove
bitfields and use typed data exclusively. Bitfields often result in
inferior machine code.
Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240423174114.526704-4-jacob.jun.pan@linux.intel.com
Link: https://lore.kernel.org/all/20240404101735.402feec8@jacob-builder/T/#mf66e34a82a48f4d8e2926b5581eff59a122de53a
|
|
To prepare native usage of posted interrupts, move the PID declarations out
of VMX code such that they can be shared.
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20240423174114.526704-2-jacob.jun.pan@linux.intel.com
|
|
Pull kvm fixes from Paolo Bonzini:
"This is a bit on the large side, mostly due to two changes:
- Changes to disable some broken PMU virtualization (see below for
details under "x86 PMU")
- Clean up SVM's enter/exit assembly code so that it can be compiled
without OBJECT_FILES_NON_STANDARD. This fixes a warning "Unpatched
return thunk in use. This should not happen!" when running KVM
selftests.
Everything else is small bugfixes and selftest changes:
- Fix a mostly benign bug in the gfn_to_pfn_cache infrastructure
where KVM would allow userspace to refresh the cache with a bogus
GPA. The bug has existed for quite some time, but was exposed by a
new sanity check added in 6.9 (to ensure a cache is either
GPA-based or HVA-based).
- Drop an unused param from gfn_to_pfn_cache_invalidate_start() that
got left behind during a 6.9 cleanup.
- Fix a math goof in x86's hugepage logic for
KVM_SET_MEMORY_ATTRIBUTES that results in an array overflow
(detected by KASAN).
- Fix a bug where KVM incorrectly clears root_role.direct when
userspace sets guest CPUID.
- Fix a dirty logging bug in the where KVM fails to write-protect
SPTEs used by a nested guest, if KVM is using Page-Modification
Logging and the nested hypervisor is NOT using EPT.
x86 PMU:
- Drop support for virtualizing adaptive PEBS, as KVM's
implementation is architecturally broken without an obvious/easy
path forward, and because exposing adaptive PEBS can leak host LBRs
to the guest, i.e. can leak host kernel addresses to the guest.
- Set the enable bits for general purpose counters in
PERF_GLOBAL_CTRL at RESET time, as done by both Intel and AMD
processors.
- Disable LBR virtualization on CPUs that don't support LBR
callstacks, as KVM unconditionally uses
PERF_SAMPLE_BRANCH_CALL_STACK when creating the perf event, and
would fail on such CPUs.
Tests:
- Fix a flaw in the max_guest_memory selftest that results in it
exhausting the supply of ucall structures when run with more than
256 vCPUs.
- Mark KVM_MEM_READONLY as supported for RISC-V in
set_memory_region_test"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (30 commits)
KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start()
KVM: selftests: Add coverage of EPT-disabled to vmx_dirty_log_test
KVM: x86/mmu: Fix and clarify comments about clearing D-bit vs. write-protecting
KVM: x86/mmu: Remove function comments above clear_dirty_{gfn_range,pt_masked}()
KVM: x86/mmu: Write-protect L2 SPTEs in TDP MMU when clearing dirty status
KVM: x86/mmu: Precisely invalidate MMU root_role during CPUID update
KVM: VMX: Disable LBR virtualization if the CPU doesn't support LBR callstacks
perf/x86/intel: Expose existence of callback support to KVM
KVM: VMX: Snapshot LBR capabilities during module initialization
KVM: x86/pmu: Do not mask LVTPC when handling a PMI on AMD platforms
KVM: x86: Snapshot if a vCPU's vendor model is AMD vs. Intel compatible
KVM: x86: Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD
KVM: SVM: Create a stack frame in __svm_sev_es_vcpu_run()
KVM: SVM: Save/restore args across SEV-ES VMRUN via host save area
KVM: SVM: Save/restore non-volatile GPRs in SEV-ES VMRUN via host save area
KVM: SVM: Clobber RAX instead of RBX when discarding spec_ctrl_intercepted
KVM: SVM: Drop 32-bit "support" from __svm_sev_es_vcpu_run()
KVM: SVM: Wrap __svm_sev_es_vcpu_run() with #ifdef CONFIG_KVM_AMD_SEV
KVM: SVM: Create a stack frame in __svm_vcpu_run() for unwinding
KVM: SVM: Remove a useless zeroing of allocated memory
...
|
|
To support TDX, KVM is enhanced to operate with #VE. For TDX, KVM uses the
suppress #VE bit in EPT entries selectively, in order to be able to trap
non-present conditions. However, #VE isn't used for VMX and it's a bug
if it happens. To be defensive and test that VMX case isn't broken
introduce an option ept_violation_ve_test and when it's set, BUG the vm.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <d6db6ba836605c0412e166359ba5c46a63c22f86.1705965635.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Dump the contents of the #VE info data structure and assert that #VE does
not happen, but do not yet do anything with it.
No functional change intended, separated for clarity only.
Extracted from a patch by Isaku Yamahata <isaku.yamahata@intel.com>.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
TDX uses different ABI to get information about VM exit. Pass intr_info to
the NMI and INTR handlers instead of pulling it from vcpu_vmx in
preparation for sharing the bulk of the handlers with TDX.
When the guest TD exits to VMM, RAX holds status and exit reason, RCX holds
exit qualification etc rather than the VMCS fields because VMM doesn't have
access to the VMCS. The eventual code will be
VMX:
- get exit reason, intr_info, exit_qualification, and etc from VMCS
- call NMI/INTR handlers (common code)
TDX:
- get exit reason, intr_info, exit_qualification, and etc from guest
registers
- call NMI/INTR handlers (common code)
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <0396a9ae70d293c9d0b060349dae385a8a4fbcec.1705965635.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
KVM accesses Virtual Machine Control Structure (VMCS) with VMX instructions
to operate on VM. TDX doesn't allow VMM to operate VMCS directly.
Instead, TDX has its own data structures, and TDX SEAMCALL APIs for VMM to
indirectly operate those data structures. This means we must have a TDX
version of kvm_x86_ops.
The existing global struct kvm_x86_ops already defines an interface which
can be adapted to TDX, but kvm_x86_ops is a system-wide, not per-VM
structure. To allow VMX to coexist with TDs, the kvm_x86_ops callbacks
will have wrappers "if (tdx) tdx_op() else vmx_op()" to pick VMX or
TDX at run time.
To split the runtime switch, the VMX implementation, and the TDX
implementation, add main.c, and move out the vmx_x86_ops hooks in
preparation for adding TDX. Use 'vt' for the naming scheme as a nod to
VT-x and as a concatenation of VmxTdx.
The eventually converted code will look like this:
vmx.c:
vmx_op() { ... }
VMX initialization
tdx.c:
tdx_op() { ... }
TDX initialization
x86_ops.h:
vmx_op();
tdx_op();
main.c:
static vt_op() { if (tdx) tdx_op() else vmx_op() }
static struct kvm_x86_ops vt_x86_ops = {
.op = vt_op,
initialization functions call both VMX and TDX initialization
Opportunistically, fix the name inconsistency from vmx_create_vcpu() and
vmx_free_vcpu() to vmx_vcpu_create() and vmx_vcpu_free().
Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Message-Id: <e603c317587f933a9d1bee8728c84e4935849c16.1705965634.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Disable LBR virtualization if the CPU doesn't support callstacks, which
were introduced in HSW (see commit e9d7f7cd97c4 ("perf/x86/intel: Add
basic Haswell LBR call stack support"), as KVM unconditionally configures
the perf LBR event with PERF_SAMPLE_BRANCH_CALL_STACK, i.e. LBR
virtualization always fails on pre-HSW CPUs.
Simply disable LBR support on such CPUs, as it has never worked, i.e.
there is no risk of breaking an existing setup, and figuring out a way
to performantly context switch LBRs on old CPUs is not worth the effort.
Fixes: be635e34c284 ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES")
Cc: Mingwei Zhang <mizhang@google.com>
Cc: Jim Mattson <jmattson@google.com>
Tested-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20240307011344.835640-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Snapshot VMX's LBR capabilities once during module initialization instead
of calling into perf every time a vCPU reconfigures its vPMU. This will
allow massaging the LBR capabilities, e.g. if the CPU doesn't support
callstacks, without having to remember to update multiple locations.
Opportunistically tag vmx_get_perf_capabilities() with __init, as it's
only called from vmx_set_cpu_caps().
Reviewed-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20240307011344.835640-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Add a WARN_ON_ONCE() sanity check to verify that a nested PML Full VM-Exit
is only synthesized when the original VM-Exit from L2 was an EPT Violation.
While KVM can fallthrough to kvm_mmu_do_page_fault() if an EPT Misconfig
occurs on a stale MMIO SPTE, KVM should not treat the access as a write
(there isn't enough information to know *what* the access was), i.e. KVM
should never try to insert a PML entry in that case.
Link: https://lore.kernel.org/r/20240209221700.393189-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Move the exit_qualification field that is used to track information about
in-flight nEPT violations from "struct kvm_vcpu_arch" to "x86_exception",
i.e. associate the information with the actual nEPT violation instead of
the vCPU. To handle bits that are pulled from vmcs.EXIT_QUALIFICATION,
i.e. that are propagated from the "original" EPT violation VM-Exit, simply
grab them from the VMCS on-demand when injecting a nEPT Violation or a PML
Full VM-exit.
Aside from being ugly, having an exit_qualification field in kvm_vcpu_arch
is outright dangerous, e.g. see commit d7f0a00e438d ("KVM: VMX: Report
up-to-date exit qualification to userspace").
Opportunstically add a comment to call out that PML Full and EPT Violation
VM-Exits use the same bit to report NMI blocking information.
Link: https://lore.kernel.org/r/20240209221700.393189-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Explicitly clear the EXIT_QUALIFCATION field when injecting an EPT
misconfig into L1, as required by the VMX architecture. Per the SDM:
This field is saved for VM exits due to the following causes:
debug exceptions; page-fault exceptions; start-up IPIs (SIPIs);
system-management interrupts (SMIs) that arrive immediately after the
execution of I/O instructions; task switches; INVEPT; INVLPG; INVPCID;
INVVPID; LGDT; LIDT; LLDT; LTR; SGDT; SIDT; SLDT; STR; VMCLEAR; VMPTRLD;
VMPTRST; VMREAD; VMWRITE; VMXON; WBINVD; WBNOINVD; XRSTORS; XSAVES;
control-register accesses; MOV DR; I/O instructions; MWAIT; accesses to
the APIC-access page; EPT violations; EOI virtualization; APIC-write
emulation; page-modification log full; SPP-related events; and
instruction timeout. For all other VM exits, this field is cleared.
Generating EXIT_QUALIFICATION from vcpu->arch.exit_qualification is wrong
for all (two) paths that lead to nested_ept_inject_page_fault(). For EPT
violations (the common case), vcpu->arch.exit_qualification will have been
set by handle_ept_violation() to vmcs02.EXIT_QUALIFICATION, i.e. contains
the information of a EPT violation and thus is likely non-zero.
For an EPT misconfig, which can reach FNAME(walk_addr_generic) and thus
inject a nEPT misconfig if KVM created an MMIO SPTE that became stale,
vcpu->arch.exit_qualification will hold the information from the last EPT
violation VM-Exit, as vcpu->arch.exit_qualification is _only_ written by
handle_ept_violation().
Fixes: 4704d0befb07 ("KVM: nVMX: Exiting from L2 to L1")
Link: https://lore.kernel.org/r/20240209221700.393189-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
allow_smaller_maxphyaddr
Use the raw/true host.MAXPHYADDR when deciding whether or not KVM must
intercept #PFs when allow_smaller_maxphyaddr is enabled, as any adjustments
the kernel makes to boot_cpu_data.x86_phys_bits to account for MKTME KeyID
bits do not apply to the guest physical address space. I.e. the KeyID are
off-limits for host physical addresses, but are not reserved for GPAs as
far as hardware is concerned.
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20240319031111.495006-1-tao1.su@linux.intel.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Drop support for virtualizing adaptive PEBS, as KVM's implementation is
architecturally broken without an obvious/easy path forward, and because
exposing adaptive PEBS can leak host LBRs to the guest, i.e. can leak
host kernel addresses to the guest.
Bug #1 is that KVM doesn't account for the upper 32 bits of
IA32_FIXED_CTR_CTRL when (re)programming fixed counters, e.g
fixed_ctrl_field() drops the upper bits, reprogram_fixed_counters()
stores local variables as u8s and truncates the upper bits too, etc.
Bug #2 is that, because KVM _always_ sets precise_ip to a non-zero value
for PEBS events, perf will _always_ generate an adaptive record, even if
the guest requested a basic record. Note, KVM will also enable adaptive
PEBS in individual *counter*, even if adaptive PEBS isn't exposed to the
guest, but this is benign as MSR_PEBS_DATA_CFG is guaranteed to be zero,
i.e. the guest will only ever see Basic records.
Bug #3 is in perf. intel_pmu_disable_fixed() doesn't clear the upper
bits either, i.e. leaves ICL_FIXED_0_ADAPTIVE set, and
intel_pmu_enable_fixed() effectively doesn't clear ICL_FIXED_0_ADAPTIVE
either. I.e. perf _always_ enables ADAPTIVE counters, regardless of what
KVM requests.
Bug #4 is that adaptive PEBS *might* effectively bypass event filters set
by the host, as "Updated Memory Access Info Group" records information
that might be disallowed by userspace via KVM_SET_PMU_EVENT_FILTER.
Bug #5 is that KVM doesn't ensure LBR MSRs hold guest values (or at least
zeros) when entering a vCPU with adaptive PEBS, which allows the guest
to read host LBRs, i.e. host RIPs/addresses, by enabling "LBR Entries"
records.
Disable adaptive PEBS support as an immediate fix due to the severity of
the LBR leak in particular, and because fixing all of the bugs will be
non-trivial, e.g. not suitable for backporting to stable kernels.
Note! This will break live migration, but trying to make KVM play nice
with live migration would be quite complicated, wouldn't be guaranteed to
work (i.e. KVM might still kill/confuse the guest), and it's not clear
that there are any publicly available VMMs that support adaptive PEBS,
let alone live migrate VMs that support adaptive PEBS, e.g. QEMU doesn't
support PEBS in any capacity.
Link: https://lore.kernel.org/all/20240306230153.786365-1-seanjc@google.com
Link: https://lore.kernel.org/all/ZeepGjHCeSfadANM@google.com
Fixes: c59a1f106f5c ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS")
Cc: stable@vger.kernel.org
Cc: Like Xu <like.xu.linux@gmail.com>
Cc: Mingwei Zhang <mizhang@google.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhang Xiong <xiong.y.zhang@intel.com>
Cc: Lv Zhiyuan <zhiyuan.lv@intel.com>
Cc: Dapeng Mi <dapeng1.mi@intel.com>
Cc: Jim Mattson <jmattson@google.com>
Acked-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20240307005833.827147-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
BHI mitigation mode spectre_bhi=auto does not deploy the software
mitigation by default. In a cloud environment, it is a likely scenario
where userspace is trusted but the guests are not trusted. Deploying
system wide mitigation in such cases is not desirable.
Update the auto mode to unconditionally mitigate against malicious
guests. Deploy the software sequence at VMexit in auto mode also, when
hardware mitigation is not available. Unlike the force =on mode,
software sequence is not deployed at syscalls in auto mode.
Suggested-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
|
|
Branch History Injection (BHI) attacks may allow a malicious application to
influence indirect branch prediction in kernel by poisoning the branch
history. eIBRS isolates indirect branch targets in ring0. The BHB can
still influence the choice of indirect branch predictor entry, and although
branch predictor entries are isolated between modes when eIBRS is enabled,
the BHB itself is not isolated between modes.
Alder Lake and new processors supports a hardware control BHI_DIS_S to
mitigate BHI. For older processors Intel has released a software sequence
to clear the branch history on parts that don't support BHI_DIS_S. Add
support to execute the software sequence at syscall entry and VMexit to
overwrite the branch history.
For now, branch history is not cleared at interrupt entry, as malicious
applications are not believed to have sufficient control over the
registers, since previous register state is cleared at interrupt
entry. Researchers continue to poke at this area and it may become
necessary to clear at interrupt entry as well in the future.
This mitigation is only defined here. It is enabled later.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Co-developed-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
|
|
Pull kvm updates from Paolo Bonzini:
"S390:
- Changes to FPU handling came in via the main s390 pull request
- Only deliver to the guest the SCLP events that userspace has
requested
- More virtual vs physical address fixes (only a cleanup since
virtual and physical address spaces are currently the same)
- Fix selftests undefined behavior
x86:
- Fix a restriction that the guest can't program a PMU event whose
encoding matches an architectural event that isn't included in the
guest CPUID. The enumeration of an architectural event only says
that if a CPU supports an architectural event, then the event can
be programmed *using the architectural encoding*. The enumeration
does NOT say anything about the encoding when the CPU doesn't
report support the event *in general*. It might support it, and it
might support it using the same encoding that made it into the
architectural PMU spec
- Fix a variety of bugs in KVM's emulation of RDPMC (more details on
individual commits) and add a selftest to verify KVM correctly
emulates RDMPC, counter availability, and a variety of other
PMC-related behaviors that depend on guest CPUID and therefore are
easier to validate with selftests than with custom guests (aka
kvm-unit-tests)
- Zero out PMU state on AMD if the virtual PMU is disabled, it does
not cause any bug but it wastes time in various cases where KVM
would check if a PMC event needs to be synthesized
- Optimize triggering of emulated events, with a nice ~10%
performance improvement in VM-Exit microbenchmarks when a vPMU is
exposed to the guest
- Tighten the check for "PMI in guest" to reduce false positives if
an NMI arrives in the host while KVM is handling an IRQ VM-Exit
- Fix a bug where KVM would report stale/bogus exit qualification
information when exiting to userspace with an internal error exit
code
- Add a VMX flag in /proc/cpuinfo to report 5-level EPT support
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock
held for read, e.g. to avoid serializing vCPUs when userspace
deletes a memslot
- Tear down TDP MMU page tables at 4KiB granularity (used to be
1GiB). KVM doesn't support yielding in the middle of processing a
zap, and 1GiB granularity resulted in multi-millisecond lags that
are quite impolite for CONFIG_PREEMPT kernels
- Allocate write-tracking metadata on-demand to avoid the memory
overhead when a kernel is built with i915 virtualization support
but the workloads use neither shadow paging nor i915 virtualization
- Explicitly initialize a variety of on-stack variables in the
emulator that triggered KMSAN false positives
- Fix the debugregs ABI for 32-bit KVM
- Rework the "force immediate exit" code so that vendor code
ultimately decides how and when to force the exit, which allowed
some optimization for both Intel and AMD
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left
elevated if vCPU creation ultimately failed, causing extra
unnecessary work
- Cleanup the logic for checking if the currently loaded vCPU is
in-kernel
- Harden against underflowing the active mmu_notifier invalidation
count, so that "bad" invalidations (usually due to bugs elsehwere
in the kernel) are detected earlier and are less likely to hang the
kernel
x86 Xen emulation:
- Overlay pages can now be cached based on host virtual address,
instead of guest physical addresses. This removes the need to
reconfigure and invalidate the cache if the guest changes the gpa
but the underlying host virtual address remains the same
- When possible, use a single host TSC value when computing the
deadline for Xen timers in order to improve the accuracy of the
timer emulation
- Inject pending upcall events when the vCPU software-enables its
APIC to fix a bug where an upcall can be lost (and to follow Xen's
behavior)
- Fall back to the slow path instead of warning if "fast" IRQ
delivery of Xen events fails, e.g. if the guest has aliased xAPIC
IDs
RISC-V:
- Support exception and interrupt handling in selftests
- New self test for RISC-V architectural timer (Sstc extension)
- New extension support (Ztso, Zacas)
- Support userspace emulation of random number seed CSRs
ARM:
- Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
- Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
- Conversion of KVM's representation of LPIs to an xarray, utilized
to address serialization some of the serialization on the LPI
injection path
- Support for _architectural_ VHE-only systems, advertised through
the absence of FEAT_E2H0 in the CPU's ID register
- Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
LoongArch:
- Set reserved bits as zero in CPUCFG
- Start SW timer only when vcpu is blocking
- Do not restart SW timer when it is expired
- Remove unnecessary CSR register saving during enter guest
- Misc cleanups and fixes as usual
Generic:
- Clean up Kconfig by removing CONFIG_HAVE_KVM, which was basically
always true on all architectures except MIPS (where Kconfig
determines the available depending on CPU capabilities). It is
replaced either by an architecture-dependent symbol for MIPS, and
IS_ENABLED(CONFIG_KVM) everywhere else
- Factor common "select" statements in common code instead of
requiring each architecture to specify it
- Remove thoroughly obsolete APIs from the uapi headers
- Move architecture-dependent stuff to uapi/asm/kvm.h
- Always flush the async page fault workqueue when a work item is
being removed, especially during vCPU destruction, to ensure that
there are no workers running in KVM code when all references to
KVM-the-module are gone, i.e. to prevent a very unlikely
use-after-free if kvm.ko is unloaded
- Grab a reference to the VM's mm_struct in the async #PF worker
itself instead of gifting the worker a reference, so that there's
no need to remember to *conditionally* clean up after the worker
Selftests:
- Reduce boilerplate especially when utilize selftest TAP
infrastructure
- Add basic smoke tests for SEV and SEV-ES, along with a pile of
library support for handling private/encrypted/protected memory
- Fix benign bugs where tests neglect to close() guest_memfd files"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits)
selftests: kvm: remove meaningless assignments in Makefiles
KVM: riscv: selftests: Add Zacas extension to get-reg-list test
RISC-V: KVM: Allow Zacas extension for Guest/VM
KVM: riscv: selftests: Add Ztso extension to get-reg-list test
RISC-V: KVM: Allow Ztso extension for Guest/VM
RISC-V: KVM: Forward SEED CSR access to user space
KVM: riscv: selftests: Add sstc timer test
KVM: riscv: selftests: Change vcpu_has_ext to a common function
KVM: riscv: selftests: Add guest helper to get vcpu id
KVM: riscv: selftests: Add exception handling support
LoongArch: KVM: Remove unnecessary CSR register saving during enter guest
LoongArch: KVM: Do not restart SW timer when it is expired
LoongArch: KVM: Start SW timer only when vcpu is blocking
LoongArch: KVM: Set reserved bits as zero in CPUCFG
KVM: selftests: Explicitly close guest_memfd files in some gmem tests
KVM: x86/xen: fix recursive deadlock in timer injection
KVM: pfncache: simplify locking and make more self-contained
KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled
KVM: x86/xen: improve accuracy of Xen timers
...
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core x86 updates from Ingo Molnar:
- The biggest change is the rework of the percpu code, to support the
'Named Address Spaces' GCC feature, by Uros Bizjak:
- This allows C code to access GS and FS segment relative memory
via variables declared with such attributes, which allows the
compiler to better optimize those accesses than the previous
inline assembly code.
- The series also includes a number of micro-optimizations for
various percpu access methods, plus a number of cleanups of %gs
accesses in assembly code.
- These changes have been exposed to linux-next testing for the
last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally working handling
of FPU switching - which also generates better code
- Propagate more RIP-relative addressing in assembly code, to generate
slightly better code
- Rework the CPU mitigations Kconfig space to be less idiosyncratic, to
make it easier for distros to follow & maintain these options
- Rework the x86 idle code to cure RCU violations and to clean up the
logic
- Clean up the vDSO Makefile logic
- Misc cleanups and fixes
* tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
x86/idle: Select idle routine only once
x86/idle: Let prefer_mwait_c1_over_halt() return bool
x86/idle: Cleanup idle_setup()
x86/idle: Clean up idle selection
x86/idle: Sanitize X86_BUG_AMD_E400 handling
sched/idle: Conditionally handle tick broadcast in default_idle_call()
x86: Increase brk randomness entropy for 64-bit systems
x86/vdso: Move vDSO to mmap region
x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
x86/retpoline: Ensure default return thunk isn't used at runtime
x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32
x86/vdso: Use $(addprefix ) instead of $(foreach )
x86/vdso: Simplify obj-y addition
x86/vdso: Consolidate targets and clean-files
x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK
x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO
x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY
x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY
x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS
...
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 FRED support from Thomas Gleixner:
"Support for x86 Fast Return and Event Delivery (FRED).
FRED is a replacement for IDT event delivery on x86 and addresses most
of the technical nightmares which IDT exposes:
1) Exception cause registers like CR2 need to be manually preserved
in nested exception scenarios.
2) Hardware interrupt stack switching is suboptimal for nested
exceptions as the interrupt stack mechanism rewinds the stack on
each entry which requires a massive effort in the low level entry
of #NMI code to handle this.
3) No hardware distinction between entry from kernel or from user
which makes establishing kernel context more complex than it needs
to be especially for unconditionally nestable exceptions like NMI.
4) NMI nesting caused by IRET unconditionally reenabling NMIs, which
is a problem when the perf NMI takes a fault when collecting a
stack trace.
5) Partial restore of ESP when returning to a 16-bit segment
6) Limitation of the vector space which can cause vector exhaustion
on large systems.
7) Inability to differentiate NMI sources
FRED addresses these shortcomings by:
1) An extended exception stack frame which the CPU uses to save
exception cause registers. This ensures that the meta information
for each exception is preserved on stack and avoids the extra
complexity of preserving it in software.
2) Hardware interrupt stack switching is non-rewinding if a nested
exception uses the currently interrupt stack.
3) The entry points for kernel and user context are separate and GS
BASE handling which is required to establish kernel context for
per CPU variable access is done in hardware.
4) NMIs are now nesting protected. They are only reenabled on the
return from NMI.
5) FRED guarantees full restore of ESP
6) FRED does not put a limitation on the vector space by design
because it uses a central entry points for kernel and user space
and the CPUstores the entry type (exception, trap, interrupt,
syscall) on the entry stack along with the vector number. The
entry code has to demultiplex this information, but this removes
the vector space restriction.
The first hardware implementations will still have the current
restricted vector space because lifting this limitation requires
further changes to the local APIC.
7) FRED stores the vector number and meta information on stack which
allows having more than one NMI vector in future hardware when the
required local APIC changes are in place.
The series implements the initial FRED support by:
- Reworking the existing entry and IDT handling infrastructure to
accomodate for the alternative entry mechanism.
- Expanding the stack frame to accomodate for the extra 16 bytes FRED
requires to store context and meta information
- Providing FRED specific C entry points for events which have
information pushed to the extended stack frame, e.g. #PF and #DB.
- Providing FRED specific C entry points for #NMI and #MCE
- Implementing the FRED specific ASM entry points and the C code to
demultiplex the events
- Providing detection and initialization mechanisms and the necessary
tweaks in context switching, GS BASE handling etc.
The FRED integration aims for maximum code reuse vs the existing IDT
implementation to the extent possible and the deviation in hot paths
like context switching are handled with alternatives to minimalize the
impact. The low level entry and exit paths are seperate due to the
extended stack frame and the hardware based GS BASE swichting and
therefore have no impact on IDT based systems.
It has been extensively tested on existing systems and on the FRED
simulation and as of now there are no outstanding problems"
* tag 'x86-fred-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (38 commits)
x86/fred: Fix init_task thread stack pointer initialization
MAINTAINERS: Add a maintainer entry for FRED
x86/fred: Fix a build warning with allmodconfig due to 'inline' failing to inline properly
x86/fred: Invoke FRED initialization code to enable FRED
x86/fred: Add FRED initialization functions
x86/syscall: Split IDT syscall setup code into idt_syscall_init()
KVM: VMX: Call fred_entry_from_kvm() for IRQ/NMI handling
x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI
x86/entry/calling: Allow PUSH_AND_CLEAR_REGS being used beyond actual entry code
x86/fred: Fixup fault on ERETU by jumping to fred_entrypoint_user
x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled
x86/traps: Add sysvec_install() to install a system interrupt handler
x86/fred: FRED entry/exit and dispatch code
x86/fred: Add a machine check entry stub for FRED
x86/fred: Add a NMI entry stub for FRED
x86/fred: Add a debug fault entry stub for FRED
x86/idtentry: Incorporate definitions/declarations of the FRED entries
x86/fred: Make exc_page_fault() work for FRED
x86/fred: Allow single-step trap and NMI when starting a new task
x86/fred: No ESPFIX needed when FRED is enabled
...
|
|
KVM x86 PMU changes for 6.9:
- Fix several bugs where KVM speciously prevents the guest from utilizing
fixed counters and architectural event encodings based on whether or not
guest CPUID reports support for the _architectural_ encoding.
- Fix a variety of bugs in KVM's emulation of RDPMC, e.g. for "fast" reads,
priority of VMX interception vs #GP, PMC types in architectural PMUs, etc.
- Add a selftest to verify KVM correctly emulates RDMPC, counter availability,
and a variety of other PMC-related behaviors that depend on guest CPUID,
i.e. are difficult to validate via KVM-Unit-Tests.
- Zero out PMU metadata on AMD if the virtual PMU is disabled to avoid wasting
cycles, e.g. when checking if a PMC event needs to be synthesized when
skipping an instruction.
- Optimize triggering of emulated events, e.g. for "count instructions" events
when skipping an instruction, which yields a ~10% performance improvement in
VM-Exit microbenchmarks when a vPMU is exposed to the guest.
- Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
|
|
KVM VMX changes for 6.9:
- Fix a bug where KVM would report stale/bogus exit qualification information
when exiting to userspace due to an unexpected VM-Exit while the CPU was
vectoring an exception.
- Add a VMX flag in /proc/cpuinfo to report 5-level EPT support.
- Clean up the logic for massaging the passthrough MSR bitmaps when userspace
changes its MSR filter.
|
|
KVM x86 misc changes for 6.9:
- Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives (though in fairness in KMSAN, it's comically
difficult to see that the uninitialized memory is never truly consumed).
- Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
DR6 and DR7.
- Rework the "force immediate exit" code so that vendor code ultimately
decides how and when to force the exit. This allows VMX to further optimize
handling preemption timer exits, and allows SVM to avoid sending a duplicate
IPI (SVM also has a need to force an exit).
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, and add WARN to guard against similar bugs.
- Provide a dedicated arch hook for checking if a different vCPU was in-kernel
(for directed yield), and simplify the logic for checking if the currently
loaded vCPU is in-kernel.
- Misc cleanups and fixes.
|
|
Combine possible_passthrough_msr_slot() and is_valid_passthrough_msr()
into a single function, vmx_get_passthrough_msr_slot(), and have the
combined helper return the slot on success, using a negative value to
indicate "failure".
Combining the operations avoids iterating over the array of passthrough
MSRs twice for relevant MSRs.
Suggested-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
The vmx_msr_filter_changed() may directly/indirectly calls only
vmx_enable_intercept_for_msr() or vmx_disable_intercept_for_msr(). Those
two functions may exit immediately if !cpu_has_vmx_msr_bitmap().
vmx_msr_filter_changed()
-> vmx_disable_intercept_for_msr()
-> pt_update_intercept_for_msr()
-> vmx_set_intercept_for_msr()
-> vmx_enable_intercept_for_msr()
-> vmx_disable_intercept_for_msr()
Therefore, we exit early if !cpu_has_vmx_msr_bitmap().
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
According to the is_valid_passthrough_msr(), the LBR MSRs are also
passthrough MSRs, since the commit 1b5ac3226a1a ("KVM: vmx/pmu:
Pass-through LBR msrs when the guest LBR event is ACTIVE").
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Now that vmx->req_immediate_exit is used only in the scope of
vmx_vcpu_run(), use force_immediate_exit to detect that KVM should usurp
the VMX preemption to force a VM-Exit and let vendor code fully handle
forcing a VM-Exit.
Opportunsitically drop __kvm_request_immediate_exit() and just have
vendor code call smp_send_reschedule() directly. SVM already does this
when injecting an event while also trying to single-step an IRET, i.e.
it's not exactly secret knowledge that KVM uses a reschedule IPI to force
an exit.
Link: https://lore.kernel.org/r/20240110012705.506918-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Eat VMX treemption timer exits in the fastpath regardless of whether L1 or
L2 is active. The VM-Exit is 100% KVM-induced, i.e. there is nothing
directly related to the exit that KVM needs to do on behalf of the guest,
thus there is no reason to wait until the slow path to do nothing.
Opportunistically add comments explaining why preemption timer exits for
emulating the guest's APIC timer need to go down the slow path.
Link: https://lore.kernel.org/r/20240110012705.506918-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Let the fastpath code decide which exits can/can't be handled in the
fastpath when L2 is active, e.g. when KVM generates a VMX preemption
timer exit to forcefully regain control, there is no "work" to be done and
so such exits can be handled in the fastpath regardless of whether L1 or
L2 is active.
Moving the is_guest_mode() check into the fastpath code also makes it
easier to see that L2 isn't allowed to use the fastpath in most cases,
e.g. it's not immediately obvious why handle_fastpath_preemption_timer()
is called from the fastpath and the normal path.
Link: https://lore.kernel.org/r/20240110012705.506918-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Handle VMX preemption timer VM-Exits due to KVM forcing an exit in the
exit fastpath, i.e. avoid calling back into handle_preemption_timer() for
the same exit. There is no work to be done for forced exits, as the name
suggests the goal is purely to get control back in KVM.
In addition to shaving a few cycles, this will allow cleanly separating
handle_fastpath_preemption_timer() from handle_preemption_timer(), e.g.
it's not immediately obvious why _apparently_ calling
handle_fastpath_preemption_timer() twice on a "slow" exit is necessary:
the "slow" call is necessary to handle exits from L2, which are excluded
from the fastpath by vmx_vcpu_run().
Link: https://lore.kernel.org/r/20240110012705.506918-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Re-enter the guest in the fast path if VMX preeemption timer VM-Exit was
"spurious", i.e. if KVM "soft disabled" the timer by writing -1u and by
some miracle the timer expired before any other VM-Exit occurred. This is
just an intermediate step to cleaning up the preemption timer handling,
optimizing these types of spurious VM-Exits is not interesting as they are
extremely rare/infrequent.
Link: https://lore.kernel.org/r/20240110012705.506918-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Annotate the kvm_entry() tracepoint with "immediate exit" when KVM is
forcing a VM-Exit immediately after VM-Enter, e.g. when KVM wants to
inject an event but needs to first complete some other operation.
Knowing that KVM is (or isn't) forcing an exit is useful information when
debugging issues related to event injection.
Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240110012705.506918-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Bite the bullet, and open code all direct reads of DR6 and DR7. KVM
currently has a mix of open coded accesses and calls to kvm_get_dr(),
which is confusing and ugly because there's no rhyme or reason as to why
any particular chunk of code uses kvm_get_dr().
The obvious alternative is to force all accesses through kvm_get_dr(),
but it's not at all clear that doing so would be a net positive, e.g. even
if KVM ends up wanting/needing to force all reads through a common helper,
e.g. to play caching games, the cost of reverting this change is likely
lower than the ongoing cost of maintaining weird, arbitrary code.
No functional change intended.
Cc: Mathias Krause <minipli@grsecurity.net>
Reviewed-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240209220752.388160-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
Convert kvm_get_dr()'s output parameter to a return value, and clean up
most of the mess that was created by forcing callers to provide a pointer.
No functional change intended.
Acked-by: Mathias Krause <minipli@grsecurity.net>
Reviewed-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240209220752.388160-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
|
|
During VMentry VERW is executed to mitigate MDS. After VERW, any memory
access like register push onto stack may put host data in MDS affected
CPU buffers. A guest can then use MDS to sample host data.
Although likelihood of secrets surviving in registers at current VERW
callsite is less, but it can't be ruled out. Harden the MDS mitigation
by moving the VERW mitigation late in VMentry path.
Note that VERW for MMIO Stale Data mitigation is unchanged because of
the complexity of per-guest conditional VERW which is not easy to handle
that late in asm with no GPRs available. If the CPU is also affected by
MDS, VERW is unconditionally executed late in asm regardless of guest
having MMIO access.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-6-a6216d83edb7%40linux.intel.com
|
|
Use EFLAGS.CF instead of EFLAGS.ZF to track whether to use VMRESUME versus
VMLAUNCH. Freeing up EFLAGS.ZF will allow doing VERW, which clobbers ZF,
for MDS mitigations as late as possible without needing to duplicate VERW
for both paths.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-5-a6216d83edb7%40linux.intel.com
|
|
The VERW mitigation at exit-to-user is enabled via a static branch
mds_user_clear. This static branch is never toggled after boot, and can
be safely replaced with an ALTERNATIVE() which is convenient to use in
asm.
Switch to ALTERNATIVE() to use the VERW mitigation late in exit-to-user
path. Also remove the now redundant VERW in exc_nmi() and
arch_exit_to_user_mode().
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-4-a6216d83edb7%40linux.intel.com
|
|
KVM x86 fixes for 6.8:
- Make a KVM_REQ_NMI request while handling KVM_SET_VCPU_EVENTS if and only
if the incoming events->nmi.pending is non-zero. If the target vCPU is in
the UNITIALIZED state, the spurious request will result in KVM exiting to
userspace, which in turn causes QEMU to constantly acquire and release
QEMU's global mutex, to the point where the BSP is unable to make forward
progress.
- Fix a type (u8 versus u64) goof that results in pmu->fixed_ctr_ctrl being
incorrectly truncated, and ultimately causes KVM to think a fixed counter
has already been disabled (KVM thinks the old value is '0').
- Fix a stack leak in KVM_GET_MSRS where a failed MSR read from userspace
that is ultimately ignored due to ignore_msrs=true doesn't zero the output
as intended.
|
|
dependent patches
Merge in pending alternatives patching infrastructure changes, before
applying more patches.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
We've had issues with gcc and 'asm goto' before, and we created a
'asm_volatile_goto()' macro for that in the past: see commits
3f0116c3238a ("compiler/gcc4: Add quirk for 'asm goto' miscompilation
bug") and a9f180345f53 ("compiler/gcc4: Make quirk for
asm_volatile_goto() unconditional").
Then, much later, we ended up removing the workaround in commit
43c249ea0b1e ("compiler-gcc.h: remove ancient workaround for gcc PR
58670") because we no longer supported building the kernel with the
affected gcc versions, but we left the macro uses around.
Now, Sean Christopherson reports a new version of a very similar
problem, which is fixed by re-applying that ancient workaround. But the
problem in question is limited to only the 'asm goto with outputs'
cases, so instead of re-introducing the old workaround as-is, let's
rename and limit the workaround to just that much less common case.
It looks like there are at least two separate issues that all hit in
this area:
(a) some versions of gcc don't mark the asm goto as 'volatile' when it
has outputs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420
which is easy to work around by just adding the 'volatile' by hand.
(b) Internal compiler errors:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422
which are worked around by adding the extra empty 'asm' as a
barrier, as in the original workaround.
but the problem Sean sees may be a third thing since it involves bad
code generation (not an ICE) even with the manually added 'volatile'.
but the same old workaround works for this case, even if this feels a
bit like voodoo programming and may only be hiding the issue.
Reported-and-tested-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Andrew Pinski <quic_apinski@quicinc.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
