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[83.57.170.65]) by smtp.gmail.com with ESMTPSA id bt14sm16070028ejb.2.2020.09.07.09.49.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Sep 2020 09:49:17 -0700 (PDT) Subject: Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP To: Claudio Fontana References: <20200903214101.1746878-1-richard.henderson@linaro.org> <20200903214101.1746878-4-richard.henderson@linaro.org> <1f573d2d-b3bb-21ab-bbcd-b759fc14ad2b@suse.de> <3dfae924-34c9-e36a-77bf-f3abcdeaf268@amsat.org> <7454d121-3ebd-623a-55a3-4ba6e7e870dc@suse.de> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Mon, 7 Sep 2020 18:49:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <7454d121-3ebd-623a-55a3-4ba6e7e870dc@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::644; envelope-from=philippe.mathieu.daude@gmail.com; helo=mail-ej1-x644.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, NICE_REPLY_A=-1.825, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, Richard Henderson , qemu-devel@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/7/20 6:30 PM, Claudio Fontana wrote: > On 9/7/20 12:20 PM, Philippe Mathieu-Daudé wrote: >> On 9/7/20 12:05 PM, Claudio Fontana wrote: >>> Hi Richard, >>> >>> currently rebasing on top of this one, >>> just a question, why is the patch not directly using "current_machine"? >> >> For user mode? > > In user mode I'd not expect softmmu/cpus.c to be built at all... Which is why :) current_machine is NULL in user-mode. > > Ciao, > > Claudio > >> >>> >>> Is using MACHINE(qdev_get_machine()) preferrable here? >>> >>> Thanks, >>> >>> Claudio >>> >>> On 9/3/20 11:40 PM, Richard Henderson wrote: >>>> Do not set parallel_cpus if there is only one cpu instantiated. >>>> This will allow tcg to use serial code to implement atomics. >>>> >>>> Reviewed-by: Philippe Mathieu-Daudé >>>> Signed-off-by: Richard Henderson >>>> --- >>>> softmmu/cpus.c | 11 ++++++++++- >>>> 1 file changed, 10 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/softmmu/cpus.c b/softmmu/cpus.c >>>> index a802e899ab..e3b98065c9 100644 >>>> --- a/softmmu/cpus.c >>>> +++ b/softmmu/cpus.c >>>> @@ -1895,6 +1895,16 @@ static void qemu_tcg_init_vcpu(CPUState *cpu) >>>> if (!tcg_region_inited) { >>>> tcg_region_inited = 1; >>>> tcg_region_init(); >>>> + /* >>>> + * If MTTCG, and we will create multiple cpus, >>>> + * then we will have cpus running in parallel. >>>> + */ >>>> + if (qemu_tcg_mttcg_enabled()) { >>>> + MachineState *ms = MACHINE(qdev_get_machine()); >>> >>> MachineState *ms = current_machine; >>> ? >>> >>> >>>> + if (ms->smp.max_cpus > 1) { >>>> + parallel_cpus = true; >>>> + } >>>> + } >>>> } >>>> >>>> if (qemu_tcg_mttcg_enabled() || !single_tcg_cpu_thread) { >>>> @@ -1904,7 +1914,6 @@ static void qemu_tcg_init_vcpu(CPUState *cpu) >>>> >>>> if (qemu_tcg_mttcg_enabled()) { >>>> /* create a thread per vCPU with TCG (MTTCG) */ >>>> - parallel_cpus = true; >>>> snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG", >>>> cpu->cpu_index); >>>> >>>> >>> >>> > >