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Returning an abort to the guest for an unsupported MMIO access is a
documented feature of the KVM UAPI. Nevertheless, it's clear that this
plumbing has seen limited testing, since userspace can trivially cause a
WARN in the MMIO return:
WARNING: CPU: 0 PID: 30558 at arch/arm64/include/asm/kvm_emulate.h:536 kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536
Call trace:
kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536
kvm_arch_vcpu_ioctl_run+0x98/0x15b4 arch/arm64/kvm/arm.c:1133
kvm_vcpu_ioctl+0x75c/0xa78 virt/kvm/kvm_main.c:4487
__do_sys_ioctl fs/ioctl.c:51 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:893
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x1e0/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x38/0x68 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x90/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
The splat is complaining that KVM is advancing PC while an exception is
pending, i.e. that KVM is retiring the MMIO instruction despite a
pending synchronous external abort. Womp womp.
Fix the glaring UAPI bug by skipping over all the MMIO emulation in
case there is a pending synchronous exception. Note that while userspace
is capable of pending an asynchronous exception (SError, IRQ, or FIQ),
it is still safe to retire the MMIO instruction in this case as (1) they
are by definition asynchronous, and (2) KVM relies on hardware support
for pending/delivering these exceptions instead of the software state
machine for advancing PC.
Cc: stable@vger.kernel.org
Fixes: da345174ceca ("KVM: arm/arm64: Allow user injection of external data aborts")
Reported-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241025203106.3529261-2-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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If a vcpu exits for a data abort with an invalid syndrome, the
expectations are that userspace has a chance to save the day if
it has requested to see such exits.
However, this is completely futile in the case of a protected VM,
as none of the state is available. In this particular case, inject
a data abort directly into the vcpu, consistent with what userspace
could do.
This also helps with pKVM, which discards all syndrome information when
forwarding data aborts that are not known to be MMIO.
Finally, document this tweak to the API.
Signed-off-by: Fuad Tabba <tabba@google.com>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240423150538.2103045-31-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
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Most exit handlers return <= 0 to indicate that the host needs to
handle the exit. Make kvm_handle_mmio_return() consistent with
the exit handlers in handle_exit(). This makes the code easier to
reason about, and makes it easier to add other handlers in future
patches.
No functional change intended.
Signed-off-by: Fuad Tabba <tabba@google.com>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240423150538.2103045-15-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
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It is a pretty well known fact that KVM does not support MMIO emulation
without valid instruction syndrome information (ESR_EL2.ISV == 0). The
current kvm_pr_unimpl() is pretty useless, as it contains zero context
to relate the event to a vCPU.
Replace it with a precise tracepoint that dumps the relevant context
so the user can make sense of what the guest is doing.
Acked-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231026205306.3045075-1-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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We currently deal with a set of booleans for VM features,
while they could be better represented as set of flags
contained in an unsigned long, similarily to what we are
doing on the CPU side.
Signed-off-by: Marc Zyngier <maz@kernel.org>
[Oliver: Flag-ify the 'ran_once' boolean]
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220311174001.605719-2-oupton@google.com
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In an effort to remove the vcpu PC manipulations from EL1 on nVHE
systems, move kvm_skip_instr() to be HYP-specific. EL1's intent
to increment PC post emulation is now signalled via a flag in the
vcpu structure.
Signed-off-by: Marc Zyngier <maz@kernel.org>
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There is no need to feed the result of kvm_vcpu_trap_il_is32bit()
to kvm_skip_instr(), as only AArch32 has a variable length ISA, and
this helper can equally be called from kvm_skip_instr32(), reducing
the complexity at all the call sites.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-next-5.6
KVM/arm64 updates for Linux 5.9:
- Split the VHE and nVHE hypervisor code bases, build the EL2 code
separately, allowing for the VHE code to now be built with instrumentation
- Level-based TLB invalidation support
- Restructure of the vcpu register storage to accomodate the NV code
- Pointer Authentication available for guests on nVHE hosts
- Simplification of the system register table parsing
- MMU cleanups and fixes
- A number of post-32bit cleanups and other fixes
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To allow for re-injection of stage-2 faults on stage-1 page-table walks
due to either a missing or read-only memslot, move the triage logic out
of io_mem_abort() and into kvm_handle_guest_abort(), where these aborts
can be handled before anything else.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20200729102821.23392-5-will@kernel.org
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In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
structure. For historical reasons, many kvm-related function parameters
retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time. This
patch does a unified cleanup of these remaining redundant parameters.
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200623131418.31473-3-tianjia.zhang@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Fix spelling and typos (e.g., repeated words) in comments.
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200401140310.29701-1-tabba@google.com
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Now that the 32bit KVM/arm host is a distant memory, let's move the
whole of the KVM/arm64 code into the arm64 tree.
As they said in the song: Welcome Home (Sanitarium).
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200513104034.74741-1-maz@kernel.org
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