From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59506) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1atHHU-0003km-EN for qemu-devel@nongnu.org; Thu, 21 Apr 2016 12:16:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1atHHR-0002GN-6z for qemu-devel@nongnu.org; Thu, 21 Apr 2016 12:16:40 -0400 Received: from mail-lf0-x22d.google.com ([2a00:1450:4010:c07::22d]:34989) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1atHHQ-0002Fa-S5 for qemu-devel@nongnu.org; Thu, 21 Apr 2016 12:16:37 -0400 Received: by mail-lf0-x22d.google.com with SMTP id c126so63868983lfb.2 for ; Thu, 21 Apr 2016 09:16:36 -0700 (PDT) References: <1460666749-24452-1-git-send-email-sergey.fedorov@linaro.org> <1460666749-24452-5-git-send-email-sergey.fedorov@linaro.org> <87inzfvwiq.fsf@linaro.org> <5714F7C4.6040306@gmail.com> <87h9eyx2e9.fsf@linaro.org> <57151EA4.7040309@gmail.com> <5718E54B.1020602@gmail.com> <87twivt0qo.fsf@linaro.org> From: Sergey Fedorov Message-ID: <5718FCE1.4050106@gmail.com> Date: Thu, 21 Apr 2016 19:16:33 +0300 MIME-Version: 1.0 In-Reply-To: <87twivt0qo.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH v3 4/4] tcg: rework tb_invalidated_flag 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 , =?UTF-8?Q?Andreas_F=c3=a4rber?= On 21/04/16 18:55, Alex Bennée wrote: > Sergey Fedorov writes: > >> On 18/04/16 20:51, Sergey Fedorov wrote: >>> On 18/04/16 20:17, Alex Bennée wrote: >>>> Sergey Fedorov writes: >>>>> On 18/04/16 17:09, Alex Bennée wrote: >>>>>> Sergey Fedorov writes: >>>>>>> diff --git a/cpu-exec.c b/cpu-exec.c >>>>> (snip) >>>>>>> @@ -507,14 +510,12 @@ int cpu_exec(CPUState *cpu) >>>>>>> } >>>>>>> tb_lock(); >>>>>>> tb = tb_find_fast(cpu); >>>>>>> - /* Note: we do it here to avoid a gcc bug on Mac OS X when >>>>>>> - doing it in tb_find_slow */ >>>>>> Is this still true? Would it make more sense to push the patching down >>>>>> to the gen_code? >>>>> This comment comes up to the commit: >>>>> >>>>> commit 1538800276aa7228d74f9d00bf275f54dc9e9b43 >>>>> Author: bellard >>>>> Date: Mon Dec 19 01:42:32 2005 +0000 >>>>> >>>>> workaround for gcc bug on PowerPC >>>>> >>>>> >>>>> It was added more than ten years ago. Anyway, now this code is here not >>>>> because of the bug: we need to reset 'next_tb' which is a local variable >>>>> in cpu_exec(). Personally, I don't think it would be neater to hide it >>>>> into gen_code(). Do you have some thoughts on how we could benefit from >>>>> doing so? BTW, I had a feeling that it may be useful to reorganize >>>>> cpu_exec() a bit, although I don't have a solid idea of how to do this >>>>> so far. >>>> I'm mainly eyeing the tb_lock/unlock which would be nice to push further >>>> down the call chain if we can, especially if the need to lock >>>> tb_find_fast can be removed later on. >>> Yes, it would be nice to possibly have all tb_lock/unlock() calls (or at >>> least their pairs) in the same block. There is a lot to be thought over :) >> It's not so simple because tb_find_fast() is also called in replay mode >> to find a TB for cpu_exec_nocache()... I'm not sure it's worth touching >> it now. > If the locking is pushed into tb_find_fast or further down is this an > issue? We would have to pass 'next_tb' (or 'last_tb' and 'tb_exit' after cleaning it up) if we move TB chaining code to tb_find_fast(). But tb_find_fast() is also called in replay mode to find a TB for cpu_exec_nocache() where we don't bother with TB chaining... Do you think it would be fine to make those changes? Kind regards, Sergey