From 9932b49e5abef0218254d15b8278e3dbee5ceea3 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Wed, 15 Apr 2020 13:34:50 -0700
Subject: [PATCH] KVM: nVMX: Invoke ept_save_pdptrs() if and only if PAE paging
is enabled
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>
---
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 13 +++++++------
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 6f303ccd478d7..5a214cbf243c0 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -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);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 19a82f846e8e2..f9bee922f1e6c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -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);
}