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KVM: MMU: Do not unconditionally read PDPTE from guest memory

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Architecturally, PDPTEs are cached in the PDPTRs when CR3 is reloaded.
On SVM, it is not possible to implement this, but on VMX this is possible
and was indeed implemented until nested SVM changed this to unconditionally
read PDPTEs dynamically.  This has noticable impact when running PAE guests.

Fix by changing the MMU to read PDPTRs from the cache, falling back to
reading from memory for the nested MMU.

Signed-off-by: Avi Kivity <avi@redhat.com>
Tested-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity
2011-07-28 11:36:17 +03:00
parent cf3ace79c0
commit e4e517b4be
5 changed files with 21 additions and 9 deletions
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5
arch/x86/kvm/mmu.c
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@ -2770,7 +2770,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
ASSERT(!VALID_PAGE(root));
if (vcpu->arch.mmu.root_level == PT32E_ROOT_LEVEL) {
pdptr = kvm_pdptr_read_mmu(vcpu, &vcpu->arch.mmu, i);
pdptr = vcpu->arch.mmu.get_pdptr(vcpu, i);
if (!is_present_gpte(pdptr)) {
vcpu->arch.mmu.pae_root[i] = 0;
continue;
@ -3318,6 +3318,7 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
context->direct_map = true;
context->set_cr3 = kvm_x86_ops->set_tdp_cr3;
context->get_cr3 = get_cr3;
context->get_pdptr = kvm_pdptr_read;
context->inject_page_fault = kvm_inject_page_fault;
context->nx = is_nx(vcpu);
@ -3376,6 +3377,7 @@ static int init_kvm_softmmu(struct kvm_vcpu *vcpu)
vcpu->arch.walk_mmu->set_cr3 = kvm_x86_ops->set_cr3;
vcpu->arch.walk_mmu->get_cr3 = get_cr3;
vcpu->arch.walk_mmu->get_pdptr = kvm_pdptr_read;
vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
return r;
@ -3386,6 +3388,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;
g_context->get_cr3 = get_cr3;
g_context->get_pdptr = kvm_pdptr_read;
g_context->inject_page_fault = kvm_inject_page_fault;
/*