From c205fb7d7d4f81e46fc577b707ceb9e356af1456 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Thu, 25 Dec 2014 02:52:16 +0200 Subject: KVM: x86: #PF error-code on R/W operations is wrong When emulating an instruction that reads the destination memory operand (i.e., instructions without the Mov flag in the emulator), the operand is first read. If a page-fault is detected in this phase, the error-code which would be delivered to the VM does not indicate that the access that caused the exception is a write one. This does not conform with real hardware, and may cause the VM to enter the page-fault handler twice for no reason (once for read, once for write). Signed-off-by: Nadav Amit Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index d949287..ef23c1e 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4909,8 +4909,12 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) /* optimisation - avoid slow emulated read if Mov */ rc = segmented_read(ctxt, ctxt->dst.addr.mem, &ctxt->dst.val, ctxt->dst.bytes); - if (rc != X86EMUL_CONTINUE) + if (rc != X86EMUL_CONTINUE) { + if (rc == X86EMUL_PROPAGATE_FAULT && + ctxt->exception.vector == PF_VECTOR) + ctxt->exception.error_code |= PFERR_WRITE_MASK; goto done; + } } ctxt->dst.orig_val = ctxt->dst.val; -- cgit v1.1