From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 08029C47DA9 for ; Tue, 30 Jan 2024 16:48:28 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rUrHL-0000q9-0F; Tue, 30 Jan 2024 11:48:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rUrHH-0000pu-7Z for qemu-devel@nongnu.org; Tue, 30 Jan 2024 11:48:03 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rUrHF-0007cU-Io for qemu-devel@nongnu.org; Tue, 30 Jan 2024 11:48:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706633280; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MFdsOWSPeNtrox5lEStOmOkO2Q9e6A/LC5tsnlQJZfg=; b=RRKd1NzNORLDQ0thpsbH84/il+KsrP71qW4GS9ZPzgZYRXKVQlcs8vCGHy0mGIC4aPGWiz 0KsfgX4hlQNZ9nAeUG9OFdiqjKm5pMaL+jzp+/UOv46vrkvcsmdU8tGr2GpL4gmKTx7K4Z fuJviEr49YOEMyfkTuoZGIzGj1LPawM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-512-ebgMphT2OsmT2Ho48_nxJw-1; Tue, 30 Jan 2024 11:47:56 -0500 X-MC-Unique: ebgMphT2OsmT2Ho48_nxJw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 30A16800074; Tue, 30 Jan 2024 16:47:56 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3E4B492BE4; Tue, 30 Jan 2024 16:47:54 +0000 (UTC) Date: Tue, 30 Jan 2024 16:47:52 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Ani Sinha Cc: Paolo Bonzini , Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum , Igor Mammedov , Julia Suvorova , qemu-devel@nongnu.org Subject: Re: [PATCH] pc: q35: Bump max_cpus to 1728 vcpus Message-ID: References: <20240130164428.35955-1-anisinha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240130164428.35955-1-anisinha@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.292, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 Tue, Jan 30, 2024 at 10:14:28PM +0530, Ani Sinha wrote: > Since commit f10a570b093e6 ("KVM: x86: Add CONFIG_KVM_MAX_NR_VCPUS to allow up to 4096 vCPUs") > Linux kernel can support upto a maximum number of 4096 vCPUS when MAXSMP is > enabled in the kernel. QEMU has been tested to correctly boot a linux guest > with 1728 vcpus both with edk2 and seabios firmwares. So bump up the max_cpus > value for q35 machines versions 9 and newer to 1728. Q35 machines versions > 8.2 and older continue to support 1024 maximum vcpus as before for > compatibility. Where does the 1728 number come from ? Did something break at 1729, or did the test machine simply not have sufficient resources to do practical larger tests ? > > If KVM is not able to support the specified number of vcpus, QEMU would > return the following error messages: > > $ ./qemu-system-x86_64 -cpu host -accel kvm -machine q35 -smp 1728 > qemu-system-x86_64: -accel kvm: warning: Number of SMP cpus requested (1728) exceeds the recommended cpus supported by KVM (12) > qemu-system-x86_64: -accel kvm: warning: Number of hotpluggable cpus requested (1728) exceeds the recommended cpus supported by KVM (12) > Number of SMP cpus requested (1728) exceeds the maximum cpus supported by KVM (1024) > > Cc: Daniel P. Berrangé > Cc: Igor Mammedov > Cc: Michael S. Tsirkin > Cc: Julia Suvorova > Signed-off-by: Ani Sinha > --- > hw/i386/pc_q35.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c > index f43d5142b8..bfa627a70b 100644 > --- a/hw/i386/pc_q35.c > +++ b/hw/i386/pc_q35.c > @@ -375,7 +375,7 @@ static void pc_q35_machine_options(MachineClass *m) > m->default_nic = "e1000e"; > m->default_kernel_irqchip_split = false; > m->no_floppy = 1; > - m->max_cpus = 1024; > + m->max_cpus = 1728; > m->no_parallel = !module_object_class_by_name(TYPE_ISA_PARALLEL); > machine_class_allow_dynamic_sysbus_dev(m, TYPE_AMD_IOMMU_DEVICE); > machine_class_allow_dynamic_sysbus_dev(m, TYPE_INTEL_IOMMU_DEVICE); > @@ -396,6 +396,7 @@ static void pc_q35_8_2_machine_options(MachineClass *m) > { > pc_q35_9_0_machine_options(m); > m->alias = NULL; > + m->max_cpus = 1024; > compat_props_add(m->compat_props, hw_compat_8_2, hw_compat_8_2_len); > compat_props_add(m->compat_props, pc_compat_8_2, pc_compat_8_2_len); > } > -- > 2.42.0 > 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 :|