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 71B66C001DE for ; Wed, 9 Aug 2023 11:15:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qTh99-00051R-SL; Wed, 09 Aug 2023 07:14:35 -0400 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 1qTh98-00051D-Ea for qemu-devel@nongnu.org; Wed, 09 Aug 2023 07:14:34 -0400 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 1qTh96-0000BQ-Ak for qemu-devel@nongnu.org; Wed, 09 Aug 2023 07:14:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691579670; h=from:from: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=IjUNeBONuhH1OoRQREkcLTbBvQRJgaEdnLzQOAx1WWQ=; b=dMzaW9Z2/EmMD1s6l+VikMcQeWcnrrKM74VtG25D32bUa4pqbMLxUZO4Xh4u46t/eg+2UA 0+nAkOowADBs3nhSJZjDll8GP0ihyNrDHOf+8ZYfiamN2j/3UV2wrLdJus/uBonViIorXs qKN98V4IS9E0vjbxiVVQqsLJJ+jzG+Y= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-592-rnrILni2PDiUTWRE5PnqjQ-1; Wed, 09 Aug 2023 07:14:29 -0400 X-MC-Unique: rnrILni2PDiUTWRE5PnqjQ-1 Received: by mail-ej1-f70.google.com with SMTP id a640c23a62f3a-99cc5d18f78so286768566b.3 for ; Wed, 09 Aug 2023 04:14:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691579668; x=1692184468; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=IjUNeBONuhH1OoRQREkcLTbBvQRJgaEdnLzQOAx1WWQ=; b=IZ+ib3vhEgIJ5WudAwzQVYnA6gGayuhImpBLHcE+tcvO45ZO3Oh0g97PEiuWqGq4iu +8+IJIVhycQfKuEk/hQbSfPuhn6UMNYM62qo1umyfMN9m0nkUdyV/dxcEimMsPvolR6Q mvDSIrSXVOwzK8n77TI5ET9uRUnG0HTPjL6Fftr4M1v9UTu8flEr3C5bv7qNAGzMpsyq sY3SZvJ1abfbqXpgS6/m1WJ4IZSkQe6qtbfKK/y25tCk9HZ8QD2Kn+2mFNu37a8pgIhv NQTSkLgMtTtYFTbJOgcu6RyQu6668tNagnaP8pEZ+76LdsTZAJRUQC8zEYsOeqoQJqSr 2mtA== X-Gm-Message-State: AOJu0YyOynpskGC86mAhjRVktPJBR1oS3xOl+8+f300L0kWkvpdO1+qE 36pL2I77hE7vjzgOAU/JC2tnRC2MZb9psex5G1r6Oikg/SgftYtluH/swaEZib6FFMdM+VMsqIq 61nxous3rV7UBgfE= X-Received: by 2002:a17:906:5daa:b0:97d:ee82:920a with SMTP id n10-20020a1709065daa00b0097dee82920amr1599489ejv.74.1691579667939; Wed, 09 Aug 2023 04:14:27 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHm9LTO701paDB9rfPYsvS6PHt3khl1sUHeNvkpWJjRMEPtzZAl7WHVLiJiRwN2q3p9hPlfEQ== X-Received: by 2002:a17:906:5daa:b0:97d:ee82:920a with SMTP id n10-20020a1709065daa00b0097dee82920amr1599479ejv.74.1691579667694; Wed, 09 Aug 2023 04:14:27 -0700 (PDT) Received: from imammedo.users.ipa.redhat.com (nat-pool-brq-t.redhat.com. [213.175.37.10]) by smtp.gmail.com with ESMTPSA id qo2-20020a170907212200b0099364d9f0e2sm7862910ejb.98.2023.08.09.04.14.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Aug 2023 04:14:27 -0700 (PDT) Date: Wed, 9 Aug 2023 13:14:26 +0200 From: Igor Mammedov To: Qian Wen Cc: qemu-devel@nongnu.org, xiaoyao.li@intel.com, zhao1.liu@intel.com, pbonzini@redhat.com, richard.henderson@linaro.org, babu.moger@amd.com Subject: Re: [PATCH v2] target/i386: Avoid cpu number overflow in legacy topology Message-ID: <20230809131426.1d9f5821@imammedo.users.ipa.redhat.com> In-Reply-To: <20230809102732.3124908-1-qian.wen@intel.com> References: <20230809102732.3124908-1-qian.wen@intel.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; 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=170.10.133.124; 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_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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 Wed, 9 Aug 2023 18:27:32 +0800 Qian Wen wrote: > The legacy topology enumerated by CPUID.1.EBX[23:16] is defined in SDM > Vol2: > > Bits 23-16: Maximum number of addressable IDs for logical processors in > this physical package. > > When launching the VM with -smp 256, the value written to EBX[23:16] is > 0 because of data overflow. If the guest only supports legacy topology, > without V2 Extended Topology enumerated by CPUID.0x1f or Extended > Topology enumerated by CPUID.0x0b to support over 255 CPUs, the return > of the kernel invoking cpu_smt_allowed() is false and AP's bring-up will > fail. Then only CPU 0 is online, and others are offline. > > To avoid this issue caused by overflow, limit the max value written to > EBX[23:16] to 255. what happens on real hw or in lack of thereof what SDM says about this value when there is more than 255 threads?. > Signed-off-by: Qian Wen > --- > Changes v1 -> v2: > - Revise the commit message and comment to more clearer. > - Rebased to v8.1.0-rc2. > --- > target/i386/cpu.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 97ad229d8b..6e1d88fbd7 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -6008,6 +6008,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, > uint32_t die_offset; > uint32_t limit; > uint32_t signature[3]; > + uint32_t threads_per_socket; > X86CPUTopoInfo topo_info; > > topo_info.dies_per_pkg = env->nr_dies; > @@ -6049,8 +6050,19 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, > *ecx |= CPUID_EXT_OSXSAVE; > } > *edx = env->features[FEAT_1_EDX]; > - if (cs->nr_cores * cs->nr_threads > 1) { > - *ebx |= (cs->nr_cores * cs->nr_threads) << 16; > + /* > + * Only bits [23:16] represent the maximum number of addressable > + * IDs for logical processors in this physical package. > + * When thread_per_socket > 255, it will 1) overwrite bits[31:24] > + * which is apic_id, 2) bits [23:16] get truncated. > + */ > + threads_per_socket = cs->nr_cores * cs->nr_threads; > + if (threads_per_socket > 255) { > + threads_per_socket = 255; > + } > + > + if (threads_per_socket > 1) { > + *ebx |= threads_per_socket << 16; > *edx |= CPUID_HT; > } > if (!cpu->enable_pmu) {