KVM: MMU: Do not unconditionally read PDPTE from guest memory
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>
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2b24a88..f043168 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1844,6 +1844,20 @@
return svm->nested.nested_cr3;
}
+static u64 nested_svm_get_tdp_pdptr(struct kvm_vcpu *vcpu, int index)
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ u64 cr3 = svm->nested.nested_cr3;
+ u64 pdpte;
+ int ret;
+
+ ret = kvm_read_guest_page(vcpu->kvm, gpa_to_gfn(cr3), &pdpte,
+ offset_in_page(cr3) + index * 8, 8);
+ if (ret)
+ return 0;
+ return pdpte;
+}
+
static void nested_svm_set_tdp_cr3(struct kvm_vcpu *vcpu,
unsigned long root)
{
@@ -1875,6 +1889,7 @@
vcpu->arch.mmu.set_cr3 = nested_svm_set_tdp_cr3;
vcpu->arch.mmu.get_cr3 = nested_svm_get_tdp_cr3;
+ vcpu->arch.mmu.get_pdptr = nested_svm_get_tdp_pdptr;
vcpu->arch.mmu.inject_page_fault = nested_svm_inject_npf_exit;
vcpu->arch.mmu.shadow_root_level = get_npt_level();
vcpu->arch.walk_mmu = &vcpu->arch.nested_mmu;
