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x86/kvm/mmu: introduce guest_mmu

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When EPT is used for nested guest we need to re-init MMU as shadow
EPT MMU (nested_ept_init_mmu_context() does that). When we return back
from L2 to L1 kvm_mmu_reset_context() in nested_vmx_load_cr3() resets
MMU back to normal TDP mode. Add a special 'guest_mmu' so we can use
separate root caches; the improved hit rate is not very important for
single vCPU performance, but it avoids contention on the mmu_lock for
many vCPUs.

On the nested CPUID benchmark, with 16 vCPUs, an L2->L1->L2 vmexit
goes from 42k to 26k cycles.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov
2018-10-08 21:28:08 +02:00
committed by Paolo Bonzini
parent 6a82cd1c7b
commit 14c07ad89f
3 changed files with 40 additions and 18 deletions
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20
arch/x86/kvm/mmu.c
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@@ -4832,7 +4832,10 @@ EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
static union kvm_mmu_page_role
kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty)
{
union kvm_mmu_page_role role = vcpu->arch.mmu->base_role;
union kvm_mmu_page_role role;
/* Role is inherited from root_mmu */
role.word = vcpu->arch.root_mmu.base_role.word;
role.level = PT64_ROOT_4LEVEL;
role.direct = false;
@@ -4982,8 +4985,10 @@ EXPORT_SYMBOL_GPL(kvm_mmu_load);
void kvm_mmu_unload(struct kvm_vcpu *vcpu)
{
kvm_mmu_free_roots(vcpu, vcpu->arch.mmu, KVM_MMU_ROOTS_ALL);
WARN_ON(VALID_PAGE(vcpu->arch.mmu->root_hpa));
kvm_mmu_free_roots(vcpu, &vcpu->arch.root_mmu, KVM_MMU_ROOTS_ALL);
WARN_ON(VALID_PAGE(vcpu->arch.root_mmu.root_hpa));
kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
WARN_ON(VALID_PAGE(vcpu->arch.guest_mmu.root_hpa));
}
EXPORT_SYMBOL_GPL(kvm_mmu_unload);
@@ -5422,13 +5427,18 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
vcpu->arch.mmu = &vcpu->arch.root_mmu;
vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
vcpu->arch.root_mmu.root_hpa = INVALID_PAGE;
vcpu->arch.root_mmu.translate_gpa = translate_gpa;
vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
vcpu->arch.root_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
vcpu->arch.guest_mmu.root_hpa = INVALID_PAGE;
vcpu->arch.guest_mmu.translate_gpa = translate_gpa;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
vcpu->arch.guest_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;
return alloc_mmu_pages(vcpu);
}