diff options
| author | Sean Christopherson <sean.j.christopherson@intel.com> | 2019-09-27 14:45:17 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-10-22 13:34:10 +0200 |
| commit | b17b7436f2f0c4984f98a0b317b8362fd365700d (patch) | |
| tree | 6c72b83c58377f085f05040d52f2385befe712e6 /arch | |
| parent | 33af3a7ef9e6fb6fa5f0168c3c67f51776dafc54 (diff) | |
KVM: VMX: Skip GUEST_CR3 VMREAD+VMWRITE if the VMCS is up-to-date
Skip the VMWRITE to update GUEST_CR3 if CR3 is not available, i.e. has
not been read from the VMCS since the last VM-Enter. If vcpu->arch.cr3
is stale, kvm_read_cr3(vcpu) will refresh vcpu->arch.cr3 from the VMCS,
meaning KVM will do a VMREAD and then VMWRITE the value it just pulled
from the VMCS.
Note, this is a purely theoretical change, no instances of skipping
the VMREAD+VMWRITE have been observed with this change.
Tested-by: Reto Buerki <reet@codelabs.ch>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 04603f53ca36..71c7a174bdaa 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3009,10 +3009,12 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) /* Loading vmcs02.GUEST_CR3 is handled by nested VM-Enter. */ if (is_guest_mode(vcpu)) update_guest_cr3 = false; - else if (enable_unrestricted_guest || is_paging(vcpu)) - guest_cr3 = kvm_read_cr3(vcpu); - else + else if (!enable_unrestricted_guest && !is_paging(vcpu)) guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr; + else if (test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail)) + guest_cr3 = vcpu->arch.cr3; + else /* vmcs01.GUEST_CR3 is already up-to-date. */ + update_guest_cr3 = false; ept_load_pdptrs(vcpu); } |