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KVM: nSVM: Use KVM-governed feature framework to track "TSC scaling enabled" 

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>
This commit is contained in:
Sean Christopherson 2023-08-15 13:36:47 -07:00
parent 7a6a6a3bf5
commit 4365a45571
4 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/kvm/governed_features.h
View File

@ -9,6 +9,7 @@ KVM_GOVERNED_X86_FEATURE(GBPAGES)
KVM_GOVERNED_X86_FEATURE(XSAVES)
KVM_GOVERNED_X86_FEATURE(VMX)
KVM_GOVERNED_X86_FEATURE(NRIPS)
KVM_GOVERNED_X86_FEATURE(TSCRATEMSR)
#undef KVM_GOVERNED_X86_FEATURE
#undef KVM_GOVERNED_FEATURE

2
arch/x86/kvm/svm/nested.c
View File

@ -695,7 +695,7 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
vmcb02->control.tsc_offset = vcpu->arch.tsc_offset;
if (svm->tsc_scaling_enabled &&
if (guest_can_use(vcpu, X86_FEATURE_TSCRATEMSR) &&
svm->tsc_ratio_msr != kvm_caps.default_tsc_scaling_ratio)
nested_svm_update_tsc_ratio_msr(vcpu);

10
arch/x86/kvm/svm/svm.c
View File

@ -2795,7 +2795,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
switch (msr_info->index) {
case MSR_AMD64_TSC_RATIO:
if (!msr_info->host_initiated && !svm->tsc_scaling_enabled)
if (!msr_info->host_initiated &&
!guest_can_use(vcpu, X86_FEATURE_TSCRATEMSR))
return 1;
msr_info->data = svm->tsc_ratio_msr;
break;
@ -2937,7 +2938,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
switch (ecx) {
case MSR_AMD64_TSC_RATIO:
if (!svm->tsc_scaling_enabled) {
if (!guest_can_use(vcpu, X86_FEATURE_TSCRATEMSR)) {
if (!msr->host_initiated)
return 1;
@ -2959,7 +2960,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
svm->tsc_ratio_msr = data;
if (svm->tsc_scaling_enabled && is_guest_mode(vcpu))
if (guest_can_use(vcpu, X86_FEATURE_TSCRATEMSR) &&
is_guest_mode(vcpu))
nested_svm_update_tsc_ratio_msr(vcpu);
break;
@ -4260,8 +4262,8 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
kvm_governed_feature_set(vcpu, X86_FEATURE_XSAVES);
kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_NRIPS);
kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_TSCRATEMSR);
svm->tsc_scaling_enabled = tsc_scaling && guest_cpuid_has(vcpu, X86_FEATURE_TSCRATEMSR);
svm->lbrv_enabled = lbrv && guest_cpuid_has(vcpu, X86_FEATURE_LBRV);
svm->v_vmload_vmsave_enabled = vls && guest_cpuid_has(vcpu, X86_FEATURE_V_VMSAVE_VMLOAD);

1
arch/x86/kvm/svm/svm.h
View File

@ -259,7 +259,6 @@ struct vcpu_svm {
bool soft_int_injected;
/* optional nested SVM features that are enabled for this guest */
bool tsc_scaling_enabled : 1;
bool v_vmload_vmsave_enabled : 1;
bool lbrv_enabled : 1;
bool pause_filter_enabled : 1;