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 9EC2DC47DA9 for ; Tue, 30 Jan 2024 19:07:57 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rUtSO-0006Bp-Ch; Tue, 30 Jan 2024 14:07:40 -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 1rUtSM-00065r-5V for qemu-devel@nongnu.org; Tue, 30 Jan 2024 14:07:38 -0500 Received: from mail-wm1-x336.google.com ([2a00:1450:4864:20::336]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1rUtSE-0000xv-IH for qemu-devel@nongnu.org; Tue, 30 Jan 2024 14:07:37 -0500 Received: by mail-wm1-x336.google.com with SMTP id 5b1f17b1804b1-40ee9e21f89so38559775e9.0 for ; Tue, 30 Jan 2024 11:07:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1706641648; x=1707246448; darn=nongnu.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=wRUt/6PYgeqfnNQFVNGZSb/yBMsHyvjdJyc5d+vIz8g=; b=e9aaQ8foeK08mds7vHWTthrWJlovuYM5wZJXKGhOyvevjpfWiCL0petdJTN4sZGCjT 8qzjTheDtw7eqwQD9M9ZESdMrXXWSzTAn0vjc+/rA5ALIMYfLI60B9TAuMW6h6xDg8GS MtnhS/k9JA7BboiWqsWw8xzjtLo5L73MBm9Hx0Ogl/7698gF9tR6U5+1Mty9p2UQhTEs ZT2RmeICfsxPmR1Tml4DdJzYZ/Pxb4r45CaHpaUIZYPDRUyktiVemdnRSP7kxJh02J/q DtbtcE0xJlrlvHFJnLac4vA9z0OltWypvfR9xVD0MW9xsyXD3M586llZaJnEYIOUx9/f ddjQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706641648; x=1707246448; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=wRUt/6PYgeqfnNQFVNGZSb/yBMsHyvjdJyc5d+vIz8g=; b=qjfZJQ7ucAjcDWmmjXHb2L103mgxcmjon4iJhWniLXQzHg74PLIfTIAU8RqamTPVjl cUtNI659oVO9zAQy0iwChSBAL7rZ4nAYtn42Hi7TpebU2M9gyDydsB0/1+q54PUYOACu roiVNeBGR3LHRXAi2zWvIVVqkH2+vG2jDUQldJcrQUHC1I7T1Xew66HUtl8BdU3fyEkY jsrCP6tUjK7FqGffF9GsAHDosZ1k6XA+yPHcxZLaG4ojMLUS1C9L5xhxRTtTIDTXvuBz vpwH5rzUJE9cab+UBXC+g9Tb24td53m68bAkGD6Fi+KQXhR9Mz2X+SGxnuPEUKIApbux JxZw== X-Gm-Message-State: AOJu0YwfkpB7Thzsy4enDnaOV7KSyZ8eFRuC/Ae6LctpkmaemNTgrmu4 QtVLxMOevhuT/9c4HPFUFsIwnxVl4aS4s+poJWrX5rj2wRKl/q+VgBV3kYGSd60= X-Google-Smtp-Source: AGHT+IFSca/1SAAEkLDJXeGjY8Wt8U5F7H21J4/A/nygTAuLlhnabrqbil/mNeWj+MnwYR8ctoaZQw== X-Received: by 2002:a05:600c:4fc9:b0:40f:20e:bf7d with SMTP id o9-20020a05600c4fc900b0040f020ebf7dmr1884671wmq.22.1706641648632; Tue, 30 Jan 2024 11:07:28 -0800 (PST) Received: from [192.168.69.100] ([176.187.218.134]) by smtp.gmail.com with ESMTPSA id p37-20020a05600c1da500b0040eee4931c9sm10773286wms.48.2024.01.30.11.07.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jan 2024 11:07:28 -0800 (PST) Message-ID: <694417c4-b976-47f7-bc61-a84a48ead117@linaro.org> Date: Tue, 30 Jan 2024 20:07:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] pc: q35: Bump max_cpus to 1728 vcpus Content-Language: en-US To: Ani Sinha , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= Cc: Paolo Bonzini , Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum , Igor Mammedov , Julia Suvorova , QEMU Developers , Gerd Hoffmann References: <20240130164428.35955-1-anisinha@redhat.com> <4CEF526A-5B22-41EA-8634-D4BB5871B739@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <4CEF526A-5B22-41EA-8634-D4BB5871B739@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::336; envelope-from=philmd@linaro.org; helo=mail-wm1-x336.google.com X-Spam_score_int: 7 X-Spam_score: 0.7 X-Spam_bar: / X-Spam_report: (0.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SCC_BODY_URI_ONLY=2.796, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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 30/1/24 18:09, Ani Sinha wrote: > > >> On 30-Jan-2024, at 22:17, Daniel P. Berrangé wrote: >> >> 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 ? > > Actual limit currently is 1856 for EDK2. The HPE folks tested QEMU with edk2 and QEMU fails to boot beyond that limit. > There are RH internal bugs tracking this and Gerd is working on it from RH side [1]. > > We would ultimately like to go to 8192 vcpus for SAP HANA but 1728 vcpus is our immediate target for now. If you want, I can resend the patch with 1856 since that is currently the tested limit. > > 1. https://issues.redhat.com/browse/RHEL-22202 Out of curiosity has the limit to be multiple of 64?