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 CE4B8C433F5 for ; Tue, 10 May 2022 08:24:14 +0000 (UTC) Received: from localhost ([::1]:40160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1noLAD-0000Jn-UZ for qemu-devel@archiver.kernel.org; Tue, 10 May 2022 04:24:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33008) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1noL0s-0001gt-1g for qemu-devel@nongnu.org; Tue, 10 May 2022 04:14:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:55268) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1noL0o-0005eo-MT for qemu-devel@nongnu.org; Tue, 10 May 2022 04:14:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652170469; 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=oThJDmoRhecfGNYeBU6b58Bud1LzaWDeIs6kGKMHRNo=; b=BUdg6JpIGwqZ+N1di/5T3MyOpSlY7sL3dA95VpjvlDjpBWPWVqvxXcYeNONd3kWw10OdLU oDyHZAqbK/FgkJlfJIH2gIjYd2Dhl1bveJj80JUg71ZCkS+IEGhGgJYl80KcJg5fQa3O+A tZOz6H/NHukaeRicC+KS3NQg4pjyeXg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-12-mwvCJAfKMsOYfrQxJLDr9Q-1; Tue, 10 May 2022 04:14:26 -0400 X-MC-Unique: mwvCJAfKMsOYfrQxJLDr9Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BFD6229ABA16; Tue, 10 May 2022 08:14:25 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.168]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A841A40CFD17; Tue, 10 May 2022 08:14:21 +0000 (UTC) Date: Tue, 10 May 2022 09:14:19 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Igor Mammedov Cc: Suravee Suthikulpanit , qemu-devel@nongnu.org, marcel.apfelbaum@gmail.com, mst@redhat.com, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, jon.grimm@amd.com Subject: Re: [PATCH] pc: q35: Bump max_cpus to 512 Message-ID: References: <20220504131639.13570-1-suravee.suthikulpanit@amd.com> <20220509091249.392fdab6@redhat.com> <20220510090325.2781238a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220510090325.2781238a@redhat.com> User-Agent: Mutt/2.1.5 (2021-12-30) X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 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: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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" On Tue, May 10, 2022 at 09:03:25AM +0200, Igor Mammedov wrote: > On Mon, 9 May 2022 13:03:38 +0100 > Daniel P. Berrangé wrote: > > > On Mon, May 09, 2022 at 09:12:49AM +0200, Igor Mammedov wrote: > > > On Wed, 4 May 2022 08:16:39 -0500 > > > Suravee Suthikulpanit wrote: > > > > > > > This is the maximum number of vCPU supported by > > > > the AMD x2APIC virtualization. > > > > > > > > Signed-off-by: Suravee Suthikulpanit > > > > --- > > > > hw/i386/pc_q35.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c > > > > index 302288342a..e82b1c690d 100644 > > > > --- a/hw/i386/pc_q35.c > > > > +++ b/hw/i386/pc_q35.c > > > > @@ -357,7 +357,7 @@ static void pc_q35_machine_options(MachineClass *m) > > > > machine_class_allow_dynamic_sysbus_dev(m, TYPE_INTEL_IOMMU_DEVICE); > > > > machine_class_allow_dynamic_sysbus_dev(m, TYPE_RAMFB_DEVICE); > > > > machine_class_allow_dynamic_sysbus_dev(m, TYPE_VMBUS_BRIDGE); > > > > - m->max_cpus = 288; > > > > + m->max_cpus = 512; > > > > > > Maybe we should bump it to KVM VCPU maximum, > > > and make sure we error out if asked for combination of > > > hardware/irqchip is not usable. > > > > In RHEL downstream we currently bump this to 710 CPUs, because you > > overflow the SMBIOS 2.1 tables at approx 720 CPUs (give/take a little > > depending on other config options). > > Also there were some testing done with 1024, > but my main reason for matching KVM's limit is unblock upstream > testing so it would be easier to push limits for others. > Downstream can clamp that value down to whatever it deems as supported. > > > Going beyond 710 CPUs value requires using the SMBIOS 3 entry point. > > > > AFAIK, the x86 machine types still default to SMBIOS 2.1, so that > > would need changing too. > > Yep, we can change default to SMBIOS 3 starting with new machine type (7.1?) > or conditionally depending on requested number of CPUs, > though I'd prefer machine type approach. Agree, machine type is better IMHO, a it gives us a consistent guest ABI regardless of CPU count. > As for SMBIOS 3, we still have to update CPU structures to support more than > 255 vcpus (Julia was working on it). It's long standing bug, but that doesn't > seem to be critical, as guest boots fine with old structures. What's the impact of SMBIOS 3 being limited to 255 ? That's lower than the current max CPUs of 288 in upstream / 710 in downstream. 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 :|