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([2a02:6b6a:b566:0:8498:f303:14d8:47b5]) by smtp.gmail.com with ESMTPSA id n3-20020a1c7203000000b003dc522dd25esm4608714wmc.30.2023.02.21.02.47.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Feb 2023 02:47:31 -0800 (PST) Message-ID: Date: Tue, 21 Feb 2023 10:47:31 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [External] Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64 Content-Language: en-US To: David Woodhouse , Oleksandr Natalenko Cc: Kim Phillips , tglx@linutronix.de, arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com, paulmck@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com, pmenzel@molgen.mpg.de, fam.zheng@bytedance.com, punit.agrawal@bytedance.com, simon.evans@bytedance.com, liangma@liangbit.com, "Limonciello, Mario" , Piotr Gorski References: <20230215145425.420125-1-usama.arif@bytedance.com> <2668869.mvXUDI8C0e@natalenko.name> <2a67f6cf18dd2c1879fad9fd8a28242918d3e5d2.camel@infradead.org> <982e1d6140705414e8fd60b990bd259a@natalenko.name> <715CBABF-4017-4784-8F30-5386F1524830@infradead.org> <67dbc69f-b712-8971-f1c9-5d07f506a19c@amd.com> <42dc683e2846ae8fc1e09715aaf7884660e1a386.camel@infradead.org> <37c18c3aeea2e558633b6da6886111d0@natalenko.name> <5A3B7074-0C6D-472B-803B-D76541828C1F@infradead.org> <3d8ed6e157df10c5175c636de0e21849@natalenko.name> <5c557f9b6f55dc2a612ee89142971298e6ae12d8.camel@infradead.org> <5b8f9c89f7015fa80c966c6c7f6fa259db6744f8.camel@infradead.org> <85ceb3f92abf3c013924de2f025517372bed19c0.camel@infradead.org> <3e5944de08ef0d23584d19bad7bae66c@natalenko.name> <26E5DC9C-0F19-4E4F-9076-04506A197374@infradead.org> From: Usama Arif In-Reply-To: <26E5DC9C-0F19-4E4F-9076-04506A197374@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/02/2023 10:27, David Woodhouse wrote: > > > On 21 February 2023 09:49:51 GMT, Oleksandr Natalenko wrote: >> On 21.02.2023 10:06, David Woodhouse wrote: >>> Why does arch/x86/kernel/acpi/sleep.c::x86_acpi_suspend_lowlevel() set >>> >>> initial_gs = per_cpu_offset(smp_processor_id()) ? >>> >>> Would it not be CPU#0 that comes back up, and should it not get >>> per_cpu_offset(0) ? >> >> Wanna me try `initial_gs = per_cpu_offset(0);` too? > I think it might be smp_processor_id() and not 0 incase CPU0 was offline at the point the system was suspended? > Hm, yes please. There's another one to make zero on the next line up, I think? > >>> Or maybe we should just set up smpboot_control for the CPU to find its >>> own stuff, *even* on waking. Since the structures are already set up, >>> it isn't like a clean boot. >>> >>> If you let it boot in parallel mode, what if you just *remove* the line >>> that sets smpboot_control=0 ? >> >> If the `smpboot_control = 0;` line in arch/x86/kernel/acpi/sleep.c::x86_acpi_suspend_lowlevel() is commented out, and the system is booted in parallel mode, then suspend/resume works. > > Well that's entertaining. Now, can we come up with any theory which doesn't leave us wondering why it ever worked in the first place...?