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Wed, 7 Jun 2023 08:33:07 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B859F477F61; Wed, 7 Jun 2023 08:33:04 +0000 (UTC) Date: Wed, 7 Jun 2023 09:33:02 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Suravee Suthikulpanit , qemu-devel@nongnu.org, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, mst@redhat.com, marcel.apfelbaum@gmail.com, imammedo@redhat.com, jusual@redhat.com, dfaggioli@suse.com, joao.m.martins@oracle.com, jon.grimm@amd.com, santosh.Shukla@amd.com Subject: Re: [PATCH v5 3/3] pc: q35: Bump max_cpus to 1024 Message-ID: References: <20230607024939.703991-1-suravee.suthikulpanit@amd.com> <20230607024939.703991-4-suravee.suthikulpanit@amd.com> <81b16f60-87d6-3043-3f1c-d77f1bf8a1c4@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <81b16f60-87d6-3043-3f1c-d77f1bf8a1c4@linaro.org> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@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_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Jun 07, 2023 at 10:26:59AM +0200, Philippe Mathieu-Daudé wrote: > On 7/6/23 04:49, Suravee Suthikulpanit wrote: > > Since KVM_MAX_VCPUS is currently defined to 1024 for x86 as shown in > > arch/x86/include/asm/kvm_host.h, update QEMU limits to the same number. > > > > In case KVM could not support the specified number of vcpus, QEMU would > > return the following error message: > > > > qemu-system-x86_64: kvm_init_vcpu: kvm_get_vcpu failed (xxx): Invalid argument > > Odd, we already check the upper limit with KVM_CAP_NR_VCPUS. > See in kvm_init(): > > /* check the vcpu limits */ > soft_vcpus_limit = kvm_recommended_vcpus(s); > hard_vcpus_limit = kvm_max_vcpus(s); > > When testing your series I get: > > qemu-system-x86_64: -accel kvm: warning: Number of SMP cpus requested (1024) > exceeds the recommended cpus supported by KVM (710) > > $ uname -srvp > Linux 5.15.0-71-generic #78-Ubuntu SMP Tue Apr 18 09:00:29 UTC 2023 x86_64 That's a relatively old kernel. With latest kernels, the 'recommended cpus' limit reported will match the number of CPUs in your host, so for me it always complains for smp > 12. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|