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Sat, 5 May 2018 13:22:14 -0400 Received: from mail-pg0-f66.google.com ([74.125.83.66]:43982 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbeEERWM (ORCPT ); Sat, 5 May 2018 13:22:12 -0400 X-Google-Smtp-Source: AB8JxZp6SETCfQg5ILcjgO+qT4EqS8ReCwGBiz7+uJmQlaXAqPtwR9XtwKFzxK9/egHRmFsOmPQdxg== Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: [PATCH] compiler-gcc: disable -ftracer for __noclone functions From: Nadav Amit In-Reply-To: <1459410252-15531-1-git-send-email-pbonzini@redhat.com> Date: Sat, 5 May 2018 10:22:10 -0700 Cc: Linux Kernel Mailing List , kvm list , lkml@tlinx.org, Andrew Morton , Michal Marek , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <6BAD64FE-CC59-40C3-9C42-90BB8EEE5453@gmail.com> References: <1459410252-15531-1-git-send-email-pbonzini@redhat.com> To: Paolo Bonzini X-Mailer: Apple Mail (2.3273) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Paolo Bonzini wrote: > -ftracer can duplicate asm blocks causing compilation to fail in > noclone functions. For example, KVM declares a global variable > in an asm like >=20 > asm("2: ... \n > .pushsection data \n > .global vmx_return \n > vmx_return: .long 2b"); >=20 > and -ftracer causes a double declaration. >=20 > Cc: Andrew Morton > Cc: Michal Marek > Cc: stable@vger.kernel.org > Cc: kvm@vger.kernel.org > Reported-by: Linda Walsh > Signed-off-by: Paolo Bonzini > --- > include/linux/compiler-gcc.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/include/linux/compiler-gcc.h = b/include/linux/compiler-gcc.h > index 22ab246feed3..eeae401a2412 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -199,7 +199,7 @@ > #define unreachable() __builtin_unreachable() >=20 > /* Mark a function definition as prohibited from being cloned. */ > -#define __noclone __attribute__((__noclone__)) > +#define __noclone __attribute__((__noclone__, = __optimize__("no-tracer"))) [ Bringing the thread back from the dead for context ] Setting different optimization attributes to certain functions = apparently prevents gcc from inlining functions with different =E2=80=9Coptimizations= =E2=80=9D. This results in poor compilation - most notably of vmx_vcpu_run() - and = causes short functions such as to_vmx() not to be inlined. Regards, Nadav=