From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59653) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1atZIw-0001qR-IX for qemu-devel@nongnu.org; Fri, 22 Apr 2016 07:31:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1atZIs-0006np-IB for qemu-devel@nongnu.org; Fri, 22 Apr 2016 07:31:22 -0400 Received: from mail-lb0-x22c.google.com ([2a00:1450:4010:c04::22c]:33104) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1atZIs-0006ni-7N for qemu-devel@nongnu.org; Fri, 22 Apr 2016 07:31:18 -0400 Received: by mail-lb0-x22c.google.com with SMTP id be4so4335517lbc.0 for ; Fri, 22 Apr 2016 04:31:18 -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> From: Sergey Fedorov Message-ID: <571A0B82.3080809@gmail.com> Date: Fri, 22 Apr 2016 14:31:14 +0300 MIME-Version: 1.0 In-Reply-To: <87mvoov2vn.fsf@linaro.org> 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: =?UTF-8?Q?Alex_Benn=c3=a9e?= Cc: Sergey Fedorov , qemu-devel@nongnu.org, Paolo Bonzini , Peter Crosthwaite , Richard Henderson , Stefan Weil 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))) Kind regards, Sergey