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>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 307e3cfa28ad..b31a3417a405 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -265,6 +265,7 @@ struct kvm_mmu {
         void (*new_cr3)(struct kvm_vcpu *vcpu);
         void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long root);
         unsigned long (*get_cr3)(struct kvm_vcpu *vcpu);
+        u64 (*get_pdptr)(struct kvm_vcpu *vcpu, int index);
         int (*page_fault)(struct kvm_vcpu *vcpu, gva_t gva, u32 err,
                           bool prefault);
         void (*inject_page_fault)(struct kvm_vcpu *vcpu,