From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47897) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ataWU-0006m1-Ml for qemu-devel@nongnu.org; Fri, 22 Apr 2016 08:49:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ataWP-0002dH-MP for qemu-devel@nongnu.org; Fri, 22 Apr 2016 08:49:26 -0400 Received: from mail-wm0-x22b.google.com ([2a00:1450:400c:c09::22b]:38486) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ataWP-0002d9-8b for qemu-devel@nongnu.org; Fri, 22 Apr 2016 08:49:21 -0400 Received: by mail-wm0-x22b.google.com with SMTP id u206so25306545wme.1 for ; Fri, 22 Apr 2016 05:49:21 -0700 (PDT) References: <1460044433-19282-1-git-send-email-sergey.fedorov@linaro.org> <1460044433-19282-4-git-send-email-sergey.fedorov@linaro.org> <87shygvcot.fsf@linaro.org> <57176AA0.2030803@gmail.com> <87mvoov2vn.fsf@linaro.org> <571A0B82.3080809@gmail.com> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <571A0B82.3080809@gmail.com> Date: Fri, 22 Apr 2016 13:49:18 +0100 Message-ID: <87mvolu7u9.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 03/11] tci: Make direct jump patching thread-safe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Sergey Fedorov Cc: Sergey Fedorov , qemu-devel@nongnu.org, Paolo Bonzini , Peter Crosthwaite , Richard Henderson , Stefan Weil Sergey Fedorov writes: > On 20/04/16 16:14, Alex Bennée wrote: >> Sergey Fedorov writes: >> >>> On 20/04/16 12:42, Alex Bennée wrote: >>>> Sergey Fedorov writes: >>>>> diff --git a/tcg/tci/tcg-target.inc.c b/tcg/tci/tcg-target.inc.c >>>>> index 4afe4d7a8d59..7e6180e62898 100644 >>>>> --- a/tcg/tci/tcg-target.inc.c >>>>> +++ b/tcg/tci/tcg-target.inc.c >>>>> @@ -556,6 +556,8 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args, >>>>> if (s->tb_jmp_offset) { >>>>> /* Direct jump method. */ >>>>> assert(args[0] < ARRAY_SIZE(s->tb_jmp_offset)); >>>>> + /* Align for atomic patching and thread safety */ >>>>> + s->code_ptr = (uint8_t *)(((uintptr_t)s->code_ptr + 3) & >>>>> ~3); >>>> Seeing this pattern is being used over and over again I wonder if we >>>> should have some utility helper functions for this? Perhaps we should >>>> steal the kernels ALIGN macros? >>> Good point, really. I see such a macro in hw/display/qxl.c and >>> kvm-all.c. It'd be better a common definition. Any idea of where to >>> put it? >> Somewhere inside include/qemu. osdep.h has ROUND_UP/DOWN functions maybe >> there makes the most sense? > > Hmm, ROUND_UP() seems to be exactly what we need here. Though I think > compiler could be smart enough to give the same code with > QEMU_ALIGN_UP() as well. But we'd benefit from something like: > > /* n-byte align pointer down */ > #define QEMU_ALIGN_PTR_DOWN(p, n) \ > ((typeof(p))QEMU_ALIGN_DOWN((uintptr_t)(p), (n))) > > /* n-byte align pointer up */ > #define QEMU_ALIGN_PTR_UP(p, n) \ > ((typeof(p))QEMU_ALIGN_UP((uintptr_t)(p), (n))) Sounds good. -- Alex Bennée