This is similar to what the EPT code does with the exit qualification.
This allows the guest to see a valid value for bits 33:32.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/paging_tmpl.h | 6 ++++++
arch/x86/kvm/svm.c | 26 ++++++++++++++++++++++----
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 410776528265..99d4c4e836a0 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -322,8 +322,14 @@ retry_walk:
real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
PFERR_USER_MASK|PFERR_WRITE_MASK);
+
+ /*
+ * Can this happen (except if the guest is playing TOCTTOU games)?
+ * We should have gotten a nested page fault on table_gfn instead.
+ */
if (unlikely(real_gfn == UNMAPPED_GVA))
goto error;
+
real_gfn = gpa_to_gfn(real_gfn);
host_addr = gfn_to_hva_prot(vcpu->kvm, real_gfn,
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8ef704037370..bd78a3baca31 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1974,10 +1974,28 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
{
struct vcpu_svm *svm = to_svm(vcpu);
- svm->vmcb->control.exit_code = SVM_EXIT_NPF;
- svm->vmcb->control.exit_code_hi = 0;
- svm->vmcb->control.exit_info_1 = fault->error_code;
- svm->vmcb->control.exit_info_2 = fault->address;
+ /*
+ * We can keep the value that the processor stored in the VMCB,
+ * but make up something sensible if we hit the WARN.
+ */
+ if (WARN_ON(svm->vmcb->control.exit_code != SVM_EXIT_NPF)) {
+ svm->vmcb->control.exit_code = SVM_EXIT_NPF;
+ svm->vmcb->control.exit_code_hi = 0;
+ svm->vmcb->control.exit_info_1 = (1ULL << 32);
+ svm->vmcb->control.exit_info_2 = fault->address;
+ }
+
+ /*
+ * The present bit is always zero for page structure faults on real
+ * hardware, but we compute it as 1 in fault->error_code. We can
+ * just keep the original exit info for page structure faults---but
+ * not for other faults, because the processor's error code might
+ * be wrong if we have just created a shadow PTE.
+ */
+ if (svm->vmcb->control.exit_info_1 & (1ULL << 32)) {
+ svm->vmcb->control.exit_info_1 &= ~0xffffffffULL;
+ svm->vmcb->control.exit_info_1 |= fault->error_code;
+ }
nested_svm_vmexit(svm);
}
--
1.8.3.1
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