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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42e70508027sm16030655e9.22.2024.09.18.05.43.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Sep 2024 05:43:11 -0700 (PDT) Date: Wed, 18 Sep 2024 14:43:09 +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: <20240918144309.5db630ff@imammedo.users.ipa.redhat.com> In-Reply-To: <4967d160-bb34-498f-8f41-d451ac590482@bytedance.com> References: <20240914110127.67690-1-xuchuangxclwt@bytedance.com> <20240918140242.2c360209@imammedo.users.ipa.redhat.com> <4967d160-bb34-498f-8f41-d451ac590482@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=UTF-8 Content-Transfer-Encoding: quoted-printable 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 20:22:26 +0800 Chuang Xu wrote: > Hi, Igor: >=20 > On 2024/9/18 =E4=B8=8B=E5=8D=888:02, Igor Mammedov wrote: > > On Sat, 14 Sep 2024 19:01:27 +0800 > > Chuang Xu wrote: > > =20 > >> When QEMU is started with: > >> -cpu host,migratable=3Don,host-cache-info=3Don,l3-cache=3Doff > >> -smp 180,sockets=3D2,dies=3D1,cores=3D45,threads=3D2 > >> > >> Execute "cpuid -1 -l 1 -r" in guest, we'll get: > >> eax=3D0x000806f8 ebx=3D0x465a0800 ecx=3D0xfffaba1f edx=3D0x3fa9fbff > >> 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=3D0xfc004121 ebx=3D0x02c0003f ecx=3D0x0000003f edx=3D0x00000000 > >> 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 disa= bled, > >> 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)=3D1" > >> 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 inte= ger > >> 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(X86CPUTo= poInfo *topo_info, > >> return num_ids - 1; > >> } > >> =20 > >> +static uint32_t max_thread_number_in_package(X86CPUTopoInfo *topo_inf= o) > >> +{ > >> + uint32_t num_threads =3D 1 << apicid_pkg_offset(topo_info); > >> + return num_threads; > >> +} > >> + > >> static uint32_t max_core_ids_in_package(X86CPUTopoInfo *topo_info) > >> { > >> uint32_t num_cores =3D 1 << (apicid_pkg_offset(topo_info) - > >> @@ -6417,7 +6423,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t in= dex, uint32_t count, > >> } > >> *edx =3D env->features[FEAT_1_EDX]; > >> if (threads_per_pkg > 1) { > >> - *ebx |=3D threads_per_pkg << 16; > >> + *ebx |=3D max_thread_number_in_package(&topo_info) << 16;= =20 > > why not use pow2ceil(threads_per_pkg) instead? =20 >=20 > I saw in the latest code that calculations of cpuids involving CPU topolo= gy all use topo_info, > so in order to maintain consistency in code style, I also used topo_info = for calculation. and we end up with a zoo of ways different topo stuff is calculated. Given we already have threads_per_pkg calculated within the function, is cleaner/more self-documenting to reuse it with pow2ceil() instead of adding yet another helper with less than obvious '1 << apicid_pkg_offset(to= po_info)' math. > > =20 > >> *edx |=3D CPUID_HT; > >> } > >> if (!cpu->enable_pmu)=20 >=20