From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH] x86, kvm: Remove incorrect redundant assembly constraint Date: Mon, 26 Nov 2012 14:48:50 -0800 Message-ID: <50B3F1D2.4010200@linux.intel.com> References: <1353537681-18759-1-git-send-email-hpa@linux.intel.com> <50B318C5.8090508@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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: Paolo Bonzini Return-path: In-Reply-To: <50B318C5.8090508@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 11/25/2012 11:22 PM, Paolo Bonzini wrote: > 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 > Gleb, Marcelo: are you going to apply this or would you prefer I took it in x86/urgent? -hpa