From 958ac3c42b683ceee9660fecb707b8d4468348ab Mon Sep 17 00:00:00 2001 From: Zhuocheng Ding Date: Tue, 24 Oct 2023 17:03:06 +0800 Subject: system/cpus: Fix CPUState.nr_cores' calculation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From CPUState.nr_cores' comment, it represents "number of cores within this CPU package". After 003f230e37d7 ("machine: Tweak the order of topology members in struct CpuTopology"), the meaning of smp.cores changed to "the number of cores in one die", but this commit missed to change CPUState.nr_cores' calculation, so that CPUState.nr_cores became wrong and now it misses to consider numbers of clusters and dies. At present, only i386 is using CPUState.nr_cores. But as for i386, which supports die level, the uses of CPUState.nr_cores are very confusing: Early uses are based on the meaning of "cores per package" (before die is introduced into i386), and later uses are based on "cores per die" (after die's introduction). This difference is due to that commit a94e1428991f ("target/i386: Add CPUID.1F generation support for multi-dies PCMachine") misunderstood that CPUState.nr_cores means "cores per die" when calculated CPUID.1FH.01H:EBX. After that, the changes in i386 all followed this wrong understanding. With the influence of 003f230e37d7 and a94e1428991f, for i386 currently the result of CPUState.nr_cores is "cores per die", thus the original uses of CPUState.cores based on the meaning of "cores per package" are wrong when multiple dies exist: 1. In cpu_x86_cpuid() of target/i386/cpu.c, CPUID.01H:EBX[bits 23:16] is incorrect because it expects "cpus per package" but now the result is "cpus per die". 2. In cpu_x86_cpuid() of target/i386/cpu.c, for all leaves of CPUID.04H: EAX[bits 31:26] is incorrect because they expect "cpus per package" but now the result is "cpus per die". The error not only impacts the EAX calculation in cache_info_passthrough case, but also impacts other cases of setting cache topology for Intel CPU according to cpu topology (specifically, the incoming parameter "num_cores" expects "cores per package" in encode_cache_cpuid4()). 3. In cpu_x86_cpuid() of target/i386/cpu.c, CPUID.0BH.01H:EBX[bits 15:00] is incorrect because the EBX of 0BH.01H (core level) expects "cpus per package", which may be different with 1FH.01H (The reason is 1FH can support more levels. For QEMU, 1FH also supports die, 1FH.01H:EBX[bits 15:00] expects "cpus per die"). 4. In cpu_x86_cpuid() of target/i386/cpu.c, when CPUID.80000001H is calculated, here "cpus per package" is expected to be checked, but in fact, now it checks "cpus per die". Though "cpus per die" also works for this code logic, this isn't consistent with AMD's APM. 5. In cpu_x86_cpuid() of target/i386/cpu.c, CPUID.80000008H:ECX expects "cpus per package" but it obtains "cpus per die". 6. In simulate_rdmsr() of target/i386/hvf/x86_emu.c, in kvm_rdmsr_core_thread_count() of target/i386/kvm/kvm.c, and in helper_rdmsr() of target/i386/tcg/sysemu/misc_helper.c, MSR_CORE_THREAD_COUNT expects "cpus per package" and "cores per package", but in these functions, it obtains "cpus per die" and "cores per die". On the other hand, these uses are correct now (they are added in/after a94e1428991f): 1. In cpu_x86_cpuid() of target/i386/cpu.c, topo_info.cores_per_die meets the actual meaning of CPUState.nr_cores ("cores per die"). 2. In cpu_x86_cpuid() of target/i386/cpu.c, vcpus_per_socket (in CPUID. 04H's calculation) considers number of dies, so it's correct. 3. In cpu_x86_cpuid() of target/i386/cpu.c, CPUID.1FH.01H:EBX[bits 15:00] needs "cpus per die" and it gets the correct result, and CPUID.1FH.02H:EBX[bits 15:00] gets correct "cpus per package". When CPUState.nr_cores is correctly changed to "cores per package" again , the above errors will be fixed without extra work, but the "currently" correct cases will go wrong and need special handling to pass correct "cpus/cores per die" they want. Fix CPUState.nr_cores' calculation to fit the original meaning "cores per package", as well as changing calculation of topo_info.cores_per_die, vcpus_per_socket and CPUID.1FH. Fixes: a94e1428991f ("target/i386: Add CPUID.1F generation support for multi-dies PCMachine") Fixes: 003f230e37d7 ("machine: Tweak the order of topology members in struct CpuTopology") Signed-off-by: Zhuocheng Ding Co-developed-by: Zhao Liu Signed-off-by: Zhao Liu Tested-by: Babu Moger Tested-by: Yongwei Ma Acked-by: Michael S. Tsirkin Message-ID: <20231024090323.1859210-4-zhao1.liu@linux.intel.com> Signed-off-by: Philippe Mathieu-Daudé --- target/i386/cpu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'target') diff --git a/target/i386/cpu.c b/target/i386/cpu.c index fc8484cb5e..358d9c0a65 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -6019,7 +6019,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, X86CPUTopoInfo topo_info; topo_info.dies_per_pkg = env->nr_dies; - topo_info.cores_per_die = cs->nr_cores; + topo_info.cores_per_die = cs->nr_cores / env->nr_dies; topo_info.threads_per_core = cs->nr_threads; /* Calculate & apply limits for different index ranges */ @@ -6095,8 +6095,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, */ if (*eax & 31) { int host_vcpus_per_cache = 1 + ((*eax & 0x3FFC000) >> 14); - int vcpus_per_socket = env->nr_dies * cs->nr_cores * - cs->nr_threads; + int vcpus_per_socket = cs->nr_cores * cs->nr_threads; if (cs->nr_cores > 1) { *eax &= ~0xFC000000; *eax |= (pow2ceil(cs->nr_cores) - 1) << 26; @@ -6273,12 +6272,12 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, break; case 1: *eax = apicid_die_offset(&topo_info); - *ebx = cs->nr_cores * cs->nr_threads; + *ebx = topo_info.cores_per_die * topo_info.threads_per_core; *ecx |= CPUID_TOPOLOGY_LEVEL_CORE; break; case 2: *eax = apicid_pkg_offset(&topo_info); - *ebx = env->nr_dies * cs->nr_cores * cs->nr_threads; + *ebx = cs->nr_cores * cs->nr_threads; *ecx |= CPUID_TOPOLOGY_LEVEL_DIE; break; default: -- cgit v1.2.3