From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] x86, kvm: Remove incorrect redundant assembly constraint Date: Mon, 26 Nov 2012 08:22:45 +0100 Message-ID: <50B318C5.8090508@redhat.com> References: <1353537681-18759-1-git-send-email-hpa@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Marcelo Tosatti , Gleb Natapov , Linux KVM mailing list , Linux Kernel Mailing List , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" To: "H. Peter Anvin" Return-path: In-Reply-To: <1353537681-18759-1-git-send-email-hpa@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Il 21/11/2012 23:41, H. Peter Anvin ha scritto: > From: "H. Peter Anvin" > > In __emulate_1op_rax_rdx, we use "+a" and "+d" which are input/output > constraints, and *then* use "a" and "d" as input constraints. This is > incorrect, but happens to work on some versions of gcc. > > However, it breaks gcc with -O0 and icc, and may break on future > versions of gcc. > > Reported-and-tested-by: Melanie Blower > Signed-off-by: H. Peter Anvin > Link: http://lkml.kernel.org/r/B3584E72CFEBED439A3ECA9BCE67A4EF1B17AF90@FMSMSX107.amr.corp.intel.com > --- > arch/x86/kvm/emulate.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 39171cb..bba39bf 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -426,8 +426,7 @@ static void invalidate_registers(struct x86_emulate_ctxt *ctxt) > _ASM_EXTABLE(1b, 3b) \ > : "=m" ((ctxt)->eflags), "=&r" (_tmp), \ > "+a" (*rax), "+d" (*rdx), "+qm"(_ex) \ > - : "i" (EFLAGS_MASK), "m" ((ctxt)->src.val), \ > - "a" (*rax), "d" (*rdx)); \ > + : "i" (EFLAGS_MASK), "m" ((ctxt)->src.val)); \ > } while (0) > > /* instruction has only one source operand, destination is implicit (e.g. mul, div, imul, idiv) */ > Reviewed-by: Paolo Bonzini