KVM: x86: emulate: correct page fault error code for NoWrite instructions

NoWrite instructions (e.g. cmp or test) never set the "write access"
bit in the error code, even if one of the operands is treated as a
destination.

Fixes: c205fb7d7d4f81e46fc577b707ceb9e356af1456
Cc: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 81dcf7964701f04b423799622260456fc8fcadf8..a943bf0c06d0d49dfed8c5f2cb87de6cacd38d94 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4954,7 +4954,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
                rc = segmented_read(ctxt, ctxt->dst.addr.mem,
                                   &ctxt->dst.val, ctxt->dst.bytes);
                if (rc != X86EMUL_CONTINUE) {
-                       if (rc == X86EMUL_PROPAGATE_FAULT &&
+                       if (!(ctxt->d & NoWrite) &&
+                           rc == X86EMUL_PROPAGATE_FAULT &&
                            ctxt->exception.vector == PF_VECTOR)
                                ctxt->exception.error_code |= PFERR_WRITE_MASK;
                        goto done;