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

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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>
This commit is contained in:
Sean Christopherson 2023-08-15 13:36:49 -07:00
parent 4d2a1560ff
commit e183d17ac3
4 changed files with 16 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

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

@ -11,6 +11,7 @@ KVM_GOVERNED_X86_FEATURE(VMX)
KVM_GOVERNED_X86_FEATURE(NRIPS)
KVM_GOVERNED_X86_FEATURE(TSCRATEMSR)
KVM_GOVERNED_X86_FEATURE(V_VMSAVE_VMLOAD)
KVM_GOVERNED_X86_FEATURE(LBRV)
#undef KVM_GOVERNED_X86_FEATURE
#undef KVM_GOVERNED_FEATURE

23
arch/x86/kvm/svm/nested.c
View file

@ -552,6 +552,7 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
bool new_vmcb12 = false;
struct vmcb *vmcb01 = svm->vmcb01.ptr;
struct vmcb *vmcb02 = svm->nested.vmcb02.ptr;
struct kvm_vcpu *vcpu = &svm->vcpu;
nested_vmcb02_compute_g_pat(svm);
@ -577,18 +578,18 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
vmcb_mark_dirty(vmcb02, VMCB_DT);
}
kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED);
kvm_set_rflags(vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED);
svm_set_efer(&svm->vcpu, svm->nested.save.efer);
svm_set_efer(vcpu, svm->nested.save.efer);
svm_set_cr0(&svm->vcpu, svm->nested.save.cr0);
svm_set_cr4(&svm->vcpu, svm->nested.save.cr4);
svm_set_cr0(vcpu, svm->nested.save.cr0);
svm_set_cr4(vcpu, svm->nested.save.cr4);
svm->vcpu.arch.cr2 = vmcb12->save.cr2;
kvm_rax_write(&svm->vcpu, vmcb12->save.rax);
kvm_rsp_write(&svm->vcpu, vmcb12->save.rsp);
kvm_rip_write(&svm->vcpu, vmcb12->save.rip);
kvm_rax_write(vcpu, vmcb12->save.rax);
kvm_rsp_write(vcpu, vmcb12->save.rsp);
kvm_rip_write(vcpu, vmcb12->save.rip);
/* In case we don't even reach vcpu_run, the fields are not updated */
vmcb02->save.rax = vmcb12->save.rax;
@ -602,7 +603,8 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
vmcb_mark_dirty(vmcb02, VMCB_DR);
}
if (unlikely(svm->lbrv_enabled && (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) {
if (unlikely(guest_can_use(vcpu, X86_FEATURE_LBRV) &&
(svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) {
/*
* Reserved bits of DEBUGCTL are ignored. Be consistent with
* svm_set_msr's definition of reserved bits.
@ -734,7 +736,7 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
vmcb02->control.virt_ext = vmcb01->control.virt_ext &
LBR_CTL_ENABLE_MASK;
if (svm->lbrv_enabled)
if (guest_can_use(vcpu, X86_FEATURE_LBRV))
vmcb02->control.virt_ext |=
(svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK);
@ -1065,7 +1067,8 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
if (!nested_exit_on_intr(svm))
kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
if (unlikely(svm->lbrv_enabled && (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) {
if (unlikely(guest_can_use(vcpu, X86_FEATURE_LBRV) &&
(svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))) {
svm_copy_lbrs(vmcb12, vmcb02);
svm_update_lbrv(vcpu);
} else if (unlikely(vmcb01->control.virt_ext & LBR_CTL_ENABLE_MASK)) {

5
arch/x86/kvm/svm/svm.c
View file

@ -1024,7 +1024,7 @@ void svm_update_lbrv(struct kvm_vcpu *vcpu)
bool current_enable_lbrv = !!(svm->vmcb->control.virt_ext &
LBR_CTL_ENABLE_MASK);
if (unlikely(is_guest_mode(vcpu) && svm->lbrv_enabled))
if (unlikely(is_guest_mode(vcpu) && guest_can_use(vcpu, X86_FEATURE_LBRV)))
if (unlikely(svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))
enable_lbrv = true;
@ -4261,8 +4261,7 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_NRIPS);
kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_TSCRATEMSR);
svm->lbrv_enabled = lbrv && guest_cpuid_has(vcpu, X86_FEATURE_LBRV);
kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_LBRV);
/*
* Intercept VMLOAD if the vCPU mode is Intel in order to emulate that

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 lbrv_enabled : 1;
bool pause_filter_enabled : 1;
bool pause_threshold_enabled : 1;
bool vgif_enabled : 1;