From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38299) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cZ1vD-0000KO-2S for qemu-devel@nongnu.org; Wed, 01 Feb 2017 15:54:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cZ1v9-000795-Qn for qemu-devel@nongnu.org; Wed, 01 Feb 2017 15:54:31 -0500 Received: from mail-pg0-x244.google.com ([2607:f8b0:400e:c05::244]:36206) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cZ1v8-00077u-3l for qemu-devel@nongnu.org; Wed, 01 Feb 2017 15:54:27 -0500 Received: by mail-pg0-x244.google.com with SMTP id 75so35184021pgf.3 for ; Wed, 01 Feb 2017 12:54:25 -0800 (PST) Sender: Paolo Bonzini References: <20170129210910.6333-1-pbonzini@redhat.com> <000601d27ba1$1f009a50$5d01cef0$@ru> From: Paolo Bonzini Message-ID: Date: Wed, 1 Feb 2017 12:54:20 -0800 MIME-Version: 1.0 In-Reply-To: <000601d27ba1$1f009a50$5d01cef0$@ru> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC/RFT PATCH 0/7] cpu-exec: simplify cpu_exec and remove some icount special cases List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pavel Dovgalyuk , qemu-devel@nongnu.org Cc: serge.fdrv@gmail.com, pavel.dovgaluk@ispras.ru, peter.maydell@linaro.org On 31/01/2017 01:05, Pavel Dovgalyuk wrote: > Hi, Paolo! > > Thanks for refactoring. > I tested these patches with icount record/replay on i386 machine. > It works, but the following changes should be applied. > I also removed call to replay_has_interrupt, because now it is not needed here. > It seems, that this call is an artifact of an older record/replay revision. > > diff --git a/cpu-exec.c b/cpu-exec.c > index 3838eb8..5cef8bc 100644 > --- a/cpu-exec.c > +++ b/cpu-exec.c > @@ -519,7 +519,8 @@ static inline bool cpu_handle_interrupt(CPUState *cpu, > } > > /* Finally, check if we need to exit to the main loop. */ > - if (unlikely(atomic_read(&cpu->exit_request) || replay_has_interrupt())) { > + if (unlikely(atomic_read(&cpu->exit_request) > + || (use_icount && cpu->icount_decr.u16.low + cpu->icount_extra == 0))) { > atomic_set(&cpu->exit_request, 0); > cpu->exception_index = EXCP_INTERRUPT; > return true; So is this needed to avoid exceptions in tb_find? Please add a comment about this and check if you can also replace: atomic_set(&cpu->exit_request, 1); in cpu_loop_exec_tb with cpu->icount_decr.u16.low = 0; ? Thanks, Paolo > Pavel Dovgalyuk > >> -----Original Message----- >> From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo Bonzini >> Sent: Monday, January 30, 2017 12:09 AM >> To: qemu-devel@nongnu.org >> Cc: serge.fdrv@gmail.com; peter.maydell@linaro.org; pavel.dovgaluk@ispras.ru >> Subject: [RFC/RFT PATCH 0/7] cpu-exec: simplify cpu_exec and remove some icount special cases >> >> The series includes three parts: >> >> 1-2: fix two bugs, the first one pretty bad, the second seems >> to be theoretical only. >> >> 3-5: simplify cpu_exec. This builds on Sergey's conversion >> of cpu_exec to a simple top-down logic, making the phases >> clearer and saving on the cost of siglongjmp in the meanwhile. >> >> 6-7: these are intended to be a base for Pavel's record/replay >> fixes. The main thing I noticed while reviewing is that icount >> is redoing (with u16.high) a lot of things that tcg_exit_req is >> doing too. This is because, at the time icount was introduced, >> tcg_exit_req didn't exist and QEMU instead unwound chained TBs >> through POSIX signals. But now we have essentially two ways to >> do the same thing with subtly different invariants or downright >> bugs (such as the one fixed by patch 1). Patch 6 therefore >> unifies tcg_exit_req and the icount interrupt flag. It saves a >> handful of instructions per TB in icount mode and generally >> makes icount mode "less special", which is a good thing since >> no one seems to understand it well. Patch 7 then removes another >> EXCP_INTERRUPT/cpu_loop_exit pair; by exiting to main loop simply >> through cpu->exit_request, hopefully it fixes one of the issues that >> Pavel was seeing. >> >> For now I've tested this only on an aarch64 Linux image (with >> and without -icount). Thanks, >> >> Paolo >> >> Paolo Bonzini (7): >> cpu-exec: fix jmp_first out-of-bounds access with icount >> cpu-exec: tighten barrier on TCG_EXIT_REQUESTED >> cpu-exec: avoid cpu_loop_exit in cpu_handle_interrupt >> cpu-exec: avoid repeated sigsetjmp on interrupts >> cpu-exec: remove outermost infinite loop >> cpu-exec: unify icount_decr and tcg_exit_req >> cpu-exec: centralize exiting to the main loop >> >> cpu-exec.c | 153 +++++++++++++++++++++------------------------- >> include/exec/exec-all.h | 1 + >> include/exec/gen-icount.h | 53 ++++++++-------- >> include/qom/cpu.h | 15 +++-- >> qom/cpu.c | 2 +- >> tcg/tcg.h | 1 - >> translate-all.c | 2 +- >> translate-common.c | 13 ++-- >> 8 files changed, 109 insertions(+), 131 deletions(-) >> >> -- >> 2.9.3 > > > >