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Switch all queries (except XSAVES) of guest features from guest CPUID to
guest capabilities, i.e. replace all calls to guest_cpuid_has() with calls
to guest_cpu_cap_has().
Keep guest_cpuid_has() around for XSAVES, but subsume its helper
guest_cpuid_get_register() and add a compile-time assertion to prevent
using guest_cpuid_has() for any other feature. Add yet another comment
for XSAVE to explain why KVM is allowed to query its raw guest CPUID.
Opportunistically drop the unused guest_cpuid_clear(), as there should be
no circumstance in which KVM needs to _clear_ a guest CPUID feature now
that everything is tracked via cpu_caps. E.g. KVM may need to _change_
a feature to emulate dynamic CPUID flags, but KVM should never need to
clear a feature in guest CPUID to prevent it from being used by the guest.
Delete the last remnants of the governed features framework, as the lone
holdout was vmx_adjust_secondary_exec_control()'s divergent behavior for
governed vs. ungoverned features.
Note, replacing guest_cpuid_has() checks with guest_cpu_cap_has() when
computing reserved CR4 bits is a nop when viewed as a whole, as KVM's
capabilities are already incorporated into the calculation, i.e. if a
feature is present in guest CPUID but unsupported by KVM, its CR4 bit
was already being marked as reserved, checking guest_cpu_cap_has() simply
double-stamps that it's a reserved bit.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-51-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Use the governed feature framework to track if Linear Address Masking (LAM)
is "enabled", i.e. if LAM can be used by the guest.
Using the framework to avoid the relative expensive call guest_cpuid_has()
during cr3 and vmexit handling paths for LAM.
No functional change intended.
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Link: https://lore.kernel.org/r/20230913124227.12574-14-binbin.wu@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "virtual NMI exposed to L1" via a governed feature flag instead of
using a dedicated bit/flag in vcpu_svm.
Note, checking KVM's capabilities instead of the "vnmi" param means that
the code isn't strictly equivalent, as vnmi_enabled could have been set
if nested=false where as that the governed feature cannot. But that's a
glorified nop as the feature/flag is consumed only by paths that are
gated by nSVM being enabled.
Link: https://lore.kernel.org/r/20230815203653.519297-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "virtual GIF exposed to L1" via a governed feature flag instead of
using a dedicated bit/flag in vcpu_svm.
Note, checking KVM's capabilities instead of the "vgif" param means that
the code isn't strictly equivalent, as vgif_enabled could have been set
if nested=false where as that the governed feature cannot. But that's a
glorified nop as the feature/flag is consumed only by paths that are
Link: https://lore.kernel.org/r/20230815203653.519297-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "Pause Filtering is exposed to L1" via governed feature flags
instead of using dedicated bits/flags in vcpu_svm.
No functional change intended.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "LBR virtualization exposed to L1" via a governed feature flag
instead of using a dedicated bit/flag in vcpu_svm.
Note, checking KVM's capabilities instead of the "lbrv" param means that
the code isn't strictly equivalent, as lbrv_enabled could have been set
if nested=false where as that the governed feature cannot. But that's a
glorified nop as the feature/flag is consumed only by paths that are
gated by nSVM being enabled.
Link: https://lore.kernel.org/r/20230815203653.519297-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "virtual VMSAVE/VMLOAD exposed to L1" via a governed feature flag
instead of using a dedicated bit/flag in vcpu_svm.
Opportunistically add a comment explaining why KVM disallows virtual
VMLOAD/VMSAVE when the vCPU model is Intel.
No functional change intended.
Link: https://lore.kernel.org/r/20230815203653.519297-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "TSC scaling exposed to L1" via a governed feature flag instead of
using a dedicated bit/flag in vcpu_svm.
Note, this fixes a benign bug where KVM would mark TSC scaling as exposed
to L1 even if overall nested SVM supported is disabled, i.e. KVM would let
L1 write MSR_AMD64_TSC_RATIO even when KVM didn't advertise TSCRATEMSR
support to userspace.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "NRIPS exposed to L1" via a governed feature flag instead of using
a dedicated bit/flag in vcpu_svm.
No functional change intended.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Track "VMX exposed to L1" via a governed feature flag instead of using a
dedicated helper to provide the same functionality. The main goal is to
drive convergence between VMX and SVM with respect to querying features
that are controllable via module param (SVM likes to cache nested
features), avoiding the guest CPUID lookups at runtime is just a bonus
and unlikely to provide any meaningful performance benefits.
Note, X86_FEATURE_VMX is set in kvm_cpu_caps if and only if "nested" is
true, and the CPU obviously supports VMX if KVM+VMX is running. I.e. the
check on "nested" is now implicitly down by the kvm_cpu_cap_has() check
in kvm_governed_feature_check_and_set().
No functional change intended.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Reviwed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Use the governed feature framework to track if XSAVES is "enabled", i.e.
if XSAVES can be used by the guest. Add a comment in the SVM code to
explain the very unintuitive logic of deliberately NOT checking if XSAVES
is enumerated in the guest CPUID model.
No functional change intended.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Use the governed feature framework to track whether or not the guest can
use 1GiB pages, and drop the one-off helper that wraps the surprisingly
non-trivial logic surrounding 1GiB page usage in the guest.
No functional change intended.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Introduce yet another X86_FEATURE flag framework to manage and cache KVM
governed features (for lack of a better name). "Governed" in this case
means that KVM has some level of involvement and/or vested interest in
whether or not an X86_FEATURE can be used by the guest. The intent of the
framework is twofold: to simplify caching of guest CPUID flags that KVM
needs to frequently query, and to add clarity to such caching, e.g. it
isn't immediately obvious that SVM's bundle of flags for "optional nested
SVM features" track whether or not a flag is exposed to L1.
Begrudgingly define KVM_MAX_NR_GOVERNED_FEATURES for the size of the
bitmap to avoid exposing governed_features.h in arch/x86/include/asm/, but
add a FIXME to call out that it can and should be cleaned up once
"struct kvm_vcpu_arch" is no longer expose to the kernel at large.
Cc: Zeng Guang <guang.zeng@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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