Commit 4365a455 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

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: default avatarYuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-10-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 7a6a6a3b

arch/x86/kvm/governed_features.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/svm/nested.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/svm/svm.c

+6 −4
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/svm/svm.h

+0 −1
Original line number Diff line number Diff line
@@ -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;