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KVM: nVMX: Invoke ept_save_pdptrs() if and only if PAE paging is enabled

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Invoke ept_save_pdptrs() when restoring L1's host state on a "late"
VM-Fail if and only if PAE paging is enabled.  This saves a CALL in the
common case where L1 is a 64-bit host, and avoids incorrectly marking
the PDPTRs as dirty.

WARN if ept_save_pdptrs() is called with PAE disabled now that the
nested usage pre-checks is_pae_paging().  Barring a bug in KVM's MMU,
attempting to read the PDPTRs with PAE disabled is now impossible.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200415203454.8296-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-04-15 13:34:50 -07:00 committed by Paolo Bonzini
parent 4dcefa312a
commit 9932b49e5a
2 changed files with 8 additions and 7 deletions
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2
arch/x86/kvm/vmx/nested.c
View File

@ -4250,7 +4250,7 @@ static void nested_vmx_restore_host_state(struct kvm_vcpu *vcpu)
* VMFail, like everything else we just need to ensure our
* software model is up-to-date.
*/
if (enable_ept)
if (enable_ept && is_pae_paging(vcpu))
ept_save_pdptrs(vcpu);
kvm_mmu_reset_context(vcpu);

13
arch/x86/kvm/vmx/vmx.c
View File

@ -2937,12 +2937,13 @@ void ept_save_pdptrs(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.walk_mmu;
if (is_pae_paging(vcpu)) {
mmu->pdptrs[0] = vmcs_read64(GUEST_PDPTR0);
mmu->pdptrs[1] = vmcs_read64(GUEST_PDPTR1);
mmu->pdptrs[2] = vmcs_read64(GUEST_PDPTR2);
mmu->pdptrs[3] = vmcs_read64(GUEST_PDPTR3);
}
if (WARN_ON_ONCE(!is_pae_paging(vcpu)))
return;
mmu->pdptrs[0] = vmcs_read64(GUEST_PDPTR0);
mmu->pdptrs[1] = vmcs_read64(GUEST_PDPTR1);
mmu->pdptrs[2] = vmcs_read64(GUEST_PDPTR2);
mmu->pdptrs[3] = vmcs_read64(GUEST_PDPTR3);
kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
}