KVM: nSVM: propagate the NPF EXITINFO to the guest

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@redhat.com>

2 files changed, 32 insertions, 4 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 410776528265..df1a044d92de 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -322,8 +322,20 @@ retry_walk:
 
                 real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
                                               PFERR_USER_MASK|PFERR_WRITE_MASK);
+
+                /*
+                 * FIXME: This can happen if emulation (for of an INS/OUTS
+                 * instruction) triggers a nested page fault.  The exit
+                 * qualification / exit info field will incorrectly have
+                 * "guest page access" as the nested page fault's cause,
+                 * instead of "guest page structure access".  To fix this,
+                 * the x86_exception struct should be augmented with enough
+                 * information to fix the exit_qualification or exit_info_1
+                 * fields.
+                 */
                 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..d0a61a05a891 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1974,10 +1974,26 @@ 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;
+        if (svm->vmcb->control.exit_code != SVM_EXIT_NPF) {
+                /*
+                 * TODO: track the cause of the nested page fault, and
+                 * correctly fill in the high bits of exit_info_1.
+                 */
+                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;
+        }
+
+        svm->vmcb->control.exit_info_1 &= ~0xffffffffULL;
+        svm->vmcb->control.exit_info_1 |= fault->error_code;
+
+        /*
+         * The present bit is always zero for page structure faults on real
+         * hardware.
+         */
+        if (svm->vmcb->control.exit_info_1 & (2ULL << 32))
+                svm->vmcb->control.exit_info_1 &= ~1;
 
         nested_svm_vmexit(svm);
 }