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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-378e73e81a5sm14367890f8f.34.2024.09.19.00.06.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2024 00:06:20 -0700 (PDT) Date: Thu, 19 Sep 2024 09:06:18 +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 v3] i386/cpu: fixup number of addressable IDs for logical processors in the physical package Message-ID: <20240919090618.463a03e4@imammedo.users.ipa.redhat.com> In-Reply-To: <20240918131815.8543-1-xuchuangxclwt@bytedance.com> References: <20240918131815.8543-1-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=170.10.133.124; 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_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 Wed, 18 Sep 2024 21:18:15 +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 > > Try to execute "cpuid -1 -l 1 -r" in guest, we'll obtain a value of 90 for > CPUID.01H.EBX[23:16], while the expected value is 128. And Try to > execute "cpuid -1 -l 4 -r" in guest, we'll obtain a value of 63 for > CPUID.04H.EAX[31:26] 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 Reviewed-by: Igor Mammedov > --- > target/i386/cpu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 4c2e6f3a71..3710ae5283 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -6417,7 +6417,7 @@ 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 |= pow2ceil(threads_per_pkg) << 16; > *edx |= CPUID_HT; > } > if (!cpu->enable_pmu) {