Commit ccf31d6e authored by Sean Christopherson's avatar Sean Christopherson
Browse files

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



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: default avatarYuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 42764413

arch/x86/kvm/cpuid.c

+17 −0
Original line number Diff line number Diff line
@@ -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))

arch/x86/kvm/governed_features.h

+2 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/mmu/mmu.c

+3 −17
Original line number Diff line number Diff line
@@ -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;