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KVM: x86/mmu: Use KVM-governed feature framework to track "GBPAGES enabled"

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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>
This commit is contained in:
Sean Christopherson 2023-08-15 13:36:40 -07:00
parent 42764413d1
commit ccf31d6e6c
3 changed files with 22 additions and 17 deletions
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17
arch/x86/kvm/cpuid.c
View File

@ -312,11 +312,28 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
struct kvm_cpuid_entry2 *best;
bool allow_gbpages;
BUILD_BUG_ON(KVM_NR_GOVERNED_FEATURES > KVM_MAX_NR_GOVERNED_FEATURES);
bitmap_zero(vcpu->arch.governed_features.enabled,
KVM_MAX_NR_GOVERNED_FEATURES);
/*
* If TDP is enabled, let the guest use GBPAGES if they're supported in
* hardware. The hardware page walker doesn't let KVM disable GBPAGES,
* i.e. won't treat them as reserved, and KVM doesn't redo the GVA->GPA
* walk for performance and complexity reasons. Not to mention KVM
* _can't_ solve the problem because GVA->GPA walks aren't visible to
* KVM once a TDP translation is installed. Mimic hardware behavior so
* that KVM's is at least consistent, i.e. doesn't randomly inject #PF.
* If TDP is disabled, honor *only* guest CPUID as KVM has full control
* and can install smaller shadow pages if the host lacks 1GiB support.
*/
allow_gbpages = tdp_enabled ? boot_cpu_has(X86_FEATURE_GBPAGES) :
guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES);
if (allow_gbpages)
kvm_governed_feature_set(vcpu, X86_FEATURE_GBPAGES);
best = kvm_find_cpuid_entry(vcpu, 1);
if (best && apic) {
if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))

2
arch/x86/kvm/governed_features.h
View File

@ -5,5 +5,7 @@ BUILD_BUG()
#define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x)
KVM_GOVERNED_X86_FEATURE(GBPAGES)
#undef KVM_GOVERNED_X86_FEATURE
#undef KVM_GOVERNED_FEATURE

20
arch/x86/kvm/mmu/mmu.c
View File

@ -4808,28 +4808,13 @@ static void __reset_rsvds_bits_mask(struct rsvd_bits_validate *rsvd_check,
}
}
static bool guest_can_use_gbpages(struct kvm_vcpu *vcpu)
{
/*
* If TDP is enabled, let the guest use GBPAGES if they're supported in
* hardware. The hardware page walker doesn't let KVM disable GBPAGES,
* i.e. won't treat them as reserved, and KVM doesn't redo the GVA->GPA
* walk for performance and complexity reasons. Not to mention KVM
* _can't_ solve the problem because GVA->GPA walks aren't visible to
* KVM once a TDP translation is installed. Mimic hardware behavior so
* that KVM's is at least consistent, i.e. doesn't randomly inject #PF.
*/
return tdp_enabled ? boot_cpu_has(X86_FEATURE_GBPAGES) :
guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES);
}
static void reset_guest_rsvds_bits_mask(struct kvm_vcpu *vcpu,
struct kvm_mmu *context)
{
__reset_rsvds_bits_mask(&context->guest_rsvd_check,
vcpu->arch.reserved_gpa_bits,
context->cpu_role.base.level, is_efer_nx(context),
guest_can_use_gbpages(vcpu),
guest_can_use(vcpu, X86_FEATURE_GBPAGES),
is_cr4_pse(context),
guest_cpuid_is_amd_or_hygon(vcpu));
}
@ -4906,7 +4891,8 @@ static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
__reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
context->root_role.level,
context->root_role.efer_nx,
guest_can_use_gbpages(vcpu), is_pse, is_amd);
guest_can_use(vcpu, X86_FEATURE_GBPAGES),
is_pse, is_amd);
if (!shadow_me_mask)
return;