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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-378e73e85ccsm12110732f8f.42.2024.09.18.05.02.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Sep 2024 05:02:44 -0700 (PDT) Date: Wed, 18 Sep 2024 14:02:42 +0200 From: Igor Mammedov To: Chuang Xu Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, xieyongji@bytedance.com, chaiwen.cc@bytedance.com, zhao1.liu@intel.com, qemu-stable@nongnu.org, Guixiong Wei , Yipeng Yin Subject: Re: [PATCH v2] i386/cpu: fixup number of addressable IDs for logical processors in the physical package Message-ID: <20240918140242.2c360209@imammedo.users.ipa.redhat.com> In-Reply-To: <20240914110127.67690-1-xuchuangxclwt@bytedance.com> References: <20240914110127.67690-1-xuchuangxclwt@bytedance.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; 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=170.10.129.124; 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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 Sat, 14 Sep 2024 19:01:27 +0800 Chuang Xu wrote: > When QEMU is started with: > -cpu host,migratable=on,host-cache-info=on,l3-cache=off > -smp 180,sockets=2,dies=1,cores=45,threads=2 > > Execute "cpuid -1 -l 1 -r" in guest, we'll get: > eax=0x000806f8 ebx=0x465a0800 ecx=0xfffaba1f edx=0x3fa9fbff > CPUID.01H.EBX[23:16] is 90, while the expected value is 128. > > Execute "cpuid -1 -l 4 -r" in guest, we'll get: > eax=0xfc004121 ebx=0x02c0003f ecx=0x0000003f edx=0x00000000 > CPUID.04H.EAX[31:26] is 63, which is as expected. > > As (1+CPUID.04H.EAX[31:26]) round up to the nearest power-of-2 integer, > we'd beter round up CPUID.01H.EBX[23:16] to the nearest power-of-2 > integer too. Otherwise we may encounter unexpected results in guest. > > For example, when QEMU is started with CLI above and xtopology is disabled, > guest kernel 5.15.120 uses CPUID.01H.EBX[23:16]/(1+CPUID.04H.EAX[31:26]) to > calculate threads-per-core in detect_ht(). Then guest will get "90/(1+63)=1" > as the result, even though theads-per-core should actually be 2. > > So let us round up CPUID.01H.EBX[23:16] to the nearest power-of-2 integer > to solve the unexpected result. > > Signed-off-by: Guixiong Wei > Signed-off-by: Yipeng Yin > Signed-off-by: Chuang Xu > --- > target/i386/cpu.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 4c2e6f3a71..24d60ead9e 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -261,6 +261,12 @@ static uint32_t max_thread_ids_for_cache(X86CPUTopoInfo *topo_info, > return num_ids - 1; > } > > +static uint32_t max_thread_number_in_package(X86CPUTopoInfo *topo_info) > +{ > + uint32_t num_threads = 1 << apicid_pkg_offset(topo_info); > + return num_threads; > +} > + > static uint32_t max_core_ids_in_package(X86CPUTopoInfo *topo_info) > { > uint32_t num_cores = 1 << (apicid_pkg_offset(topo_info) - > @@ -6417,7 +6423,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, > } > *edx = env->features[FEAT_1_EDX]; > if (threads_per_pkg > 1) { > - *ebx |= threads_per_pkg << 16; > + *ebx |= max_thread_number_in_package(&topo_info) << 16; why not use pow2ceil(threads_per_pkg) instead? > *edx |= CPUID_HT; > } > if (!cpu->enable_pmu) {