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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3680daccc9csm9331403f8f.57.2024.07.16.08.21.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jul 2024 08:21:26 -0700 (PDT) Date: Tue, 16 Jul 2024 17:21:25 +0200 From: Igor Mammedov To: Salil Mehta Cc: Salil Mehta , "qemu-devel@nongnu.org" , "maz@kernel.org" , "jean-philippe@linaro.org" , Jonathan Cameron , "lpieralisi@kernel.org" , "peter.maydell@linaro.org" , "richard.henderson@linaro.org" , "andrew.jones@linux.dev" , "david@redhat.com" , "philmd@linaro.org" , "eric.auger@redhat.com" , "oliver.upton@linux.dev" , "pbonzini@redhat.com" , "mst@redhat.com" , "will@kernel.org" , "gshan@redhat.com" , "rafael@kernel.org" , "alex.bennee@linaro.org" , "linux@armlinux.org.uk" , "darren@os.amperecomputing.com" , "ilkka@os.amperecomputing.com" , "vishnu@os.amperecomputing.com" , "karl.heubaum@oracle.com" , "miguel.luis@oracle.com" , zhukeqian , "wangxiongfeng (C)" , "wangyanan (Y)" , "jiakernel2@gmail.com" , "maobibo@loongson.cn" , "lixianglai@loongson.cn" , "npiggin@gmail.com" , "harshpb@linux.ibm.com" , Linuxarm , "peterx@redhat.com" Subject: Re: [PATCH V15 0/7] Add architecture agnostic code to support vCPU Hotplug Message-ID: <20240716172125.0b1fd791@imammedo.users.ipa.redhat.com> In-Reply-To: References: <20240713182516.1457-1-salil.mehta@huawei.com> <20240715155436.577d34c5@imammedo.users.ipa.redhat.com> <3848723ea2584b9b813c3d76e1e6dd59@huawei.com> <20240715171154.2667d187@imammedo.users.ipa.redhat.com> <4b829bf1-d31c-49eb-b18f-6d87e08c5c04@opnsrc.net> <20240716115210.08ca24ba@imammedo.users.ipa.redhat.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, 16 Jul 2024 11:43:00 +0000 Salil Mehta wrote: > Hi Igor, > > > From: Igor Mammedov > > Sent: Tuesday, July 16, 2024 10:52 AM > > To: Salil Mehta > > > > On Tue, 16 Jul 2024 03:38:29 +0000 > > Salil Mehta wrote: > > > > > Hi Igor, > > > > > > On 15/07/2024 15:11, Igor Mammedov wrote: > > > > On Mon, 15 Jul 2024 14:19:12 +0000 > > > > Salil Mehta wrote: > > > > > > > >>> From: qemu-arm-bounces+salil.mehta=huawei.com@nongnu.org > > >>> arm-bounces+salil.mehta=huawei.com@nongnu.org> On Behalf Of Salil > > > >>> Mehta via > > > >>> Sent: Monday, July 15, 2024 3:14 PM > > > >>> To: Igor Mammedov > > > >>> > > > >>> Hi Igor, > > > >>> > > > >>> > From: Igor Mammedov > > > >>> > Sent: Monday, July 15, 2024 2:55 PM > > > >>> > To: Salil Mehta > > > >>> > > > > >>> > On Sat, 13 Jul 2024 19:25:09 +0100 > > > >>> > Salil Mehta wrote: > > > >>> > > > > >>> > > [Note: References are present at the last after the revision > > > >>> > history] > > Virtual CPU hotplug support is being added across > > > >>> > various architectures [1][3]. > > > >>> > > This series adds various code bits common across all architectures: > > > >>> > > > > > >>> > > 1. vCPU creation and Parking code refactor [Patch 1] 2. Update ACPI > > > >>> > > GED framework to support vCPU Hotplug [Patch 2,3] 3. ACPI CPUs AML > > > >>> > > code change [Patch 4,5] 4. Helper functions to support unrealization > > > >>> > > of CPU objects [Patch 6,7] > > > >>> > > > > >>> > with patch 1 and 3 fixed should be good to go. > > > >>> > > > > >>> > Salil, > > > >>> > Can you remind me what happened to migration part of this? > > > >>> > Ideally it should be a part of of this series as it should be common > > > >>> > for everything that uses GED and should be a conditional part of > > > >>> > GED's VMSTATE. > > > >>> > > > > >>> > If this series is just a common base and no actual hotplug on top of > > > >>> > it is merged in this release (provided patch 13 is fixed), I'm fine > > > >>> > with migration bits being a separate series on top. > > > >>> > > > > >>> > However if some machine would be introducing cpu hotplug in the same > > > >>> > release, then the migration part should be merged before it or be a > > > >>> > part that cpu hotplug series. > > > >>> > > > >>> We have tested Live/Pseudo Migration and it seem to work with the > > > >>> changes part of the architecture specific patch-set. > > > > > > > > have you tested, migration from new QEMU to an older one (that doesn't have cpuhotplug builtin)? > > > > > > > > > Just curious, how can we detect at source Qemu what version of the > > > Qemu destination is running. We require some sort of compatibility > > > check but then this is a problem not specific to CPU Hotplug? > > > > it's usually managed by version machine types + compat settings for > > machine/device. > > Ok. it looks to be a static checking at the source. I'm sure there must be > a way to dynamically do the same by negotiating the features i.e. only > enabling the common subset at the destination. I quickly skimmed the > migration code and I cannot find any thing like this being done as of now. > And this problem looks to be a pandoras box to me. no dynamic negotiating as far as I'm aware. We've managed to survive so far with static compat knobs (with an occasional disaster along the way) ... > > Thanks > Salil. >