Re: [PATCH RESEND 05/18] i386/cpu: Consolidate the use of topo_info in cpu_x86_cpuid()

[wangyanan (Y)]

在 2023/2/13 17:36, Zhao Liu 写道:
> From: Zhao Liu <zhao1.liu@intel.com>
>
> In cpu_x86_cpuid(), there are many variables in representing the cpu
> topology, e.g., topo_info, cs->nr_cores/cs->nr_threads.
>
> Since the names of cs->nr_cores/cs->nr_threads does not accurately
> represent its meaning, the use of cs->nr_cores/cs->nr_threads is prone
> to confusion and mistakes.
>
> And the structure X86CPUTopoInfo names its memebers clearly, thus the
> variable "topo_info" should be preferred.
>
> Suggested-by: Robert Hoo <robert.hu@linux.intel.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   target/i386/cpu.c | 30 ++++++++++++++++++------------
>   1 file changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 7833505092d8..4cda84eb96f1 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5215,11 +5215,15 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>       uint32_t limit;
>       uint32_t signature[3];
>       X86CPUTopoInfo topo_info;
> +    uint32_t cpus_per_pkg;
>   
>       topo_info.dies_per_pkg = env->nr_dies;
>       topo_info.cores_per_die = cs->nr_cores / env->nr_dies;
>       topo_info.threads_per_core = cs->nr_threads;
>   
> +    cpus_per_pkg = topo_info.dies_per_pkg * topo_info.cores_per_die *
> +                   topo_info.threads_per_core;
> +
>       /* Calculate & apply limits for different index ranges */
>       if (index >= 0xC0000000) {
>           limit = env->cpuid_xlevel2;
> @@ -5255,8 +5259,8 @@ 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;
> +        if (cpus_per_pkg > 1) {
> +            *ebx |= cpus_per_pkg << 16;
>               *edx |= CPUID_HT;
>           }
>           if (!cpu->enable_pmu) {
> @@ -5293,10 +5297,12 @@ 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 = cs->nr_cores * cs->nr_threads;
> -                if (cs->nr_cores > 1) {
> +                int vcpus_per_socket = cpus_per_pkg;
Would it make sense to directly use cpus_per_pkg here
> +                int cores_per_socket = topo_info.cores_per_die *
> +                                       topo_info.dies_per_pkg;
There are other places in cpu_x86_cpuid where cs->nr_cores is used
separately, why not make a global "cores_per_pkg" like cpus_per_pkg
and also tweak the other places?
> +                if (cores_per_socket > 1) {
>                       *eax &= ~0xFC000000;
> -                    *eax |= (pow2ceil(cs->nr_cores) - 1) << 26;
> +                    *eax |= (pow2ceil(cores_per_socket) - 1) << 26;
>                   }
>                   if (host_vcpus_per_cache > vcpus_per_socket) {
>                       *eax &= ~0x3FFC000;
> @@ -5436,12 +5442,12 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>           switch (count) {
>           case 0:
>               *eax = apicid_core_offset(&topo_info);
> -            *ebx = cs->nr_threads;
> +            *ebx = topo_info.threads_per_core;
There are many other places in cpu_x86_cpuid where cs->nr_threads
is used separately, such as encode_cache_cpuid4(***), should we
replace them all?
>               *ecx |= CPUID_TOPOLOGY_LEVEL_SMT;
>               break;
>           case 1:
>               *eax = apicid_pkg_offset(&topo_info);
> -            *ebx = cs->nr_cores * cs->nr_threads;
> +            *ebx = cpus_per_pkg;
>               *ecx |= CPUID_TOPOLOGY_LEVEL_CORE;
>               break;
>           default:
> @@ -5472,7 +5478,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>           switch (count) {
>           case 0:
>               *eax = apicid_core_offset(&topo_info);
> -            *ebx = cs->nr_threads;
> +            *ebx = topo_info.threads_per_core;
>               *ecx |= CPUID_TOPOLOGY_LEVEL_SMT;
>               break;
>           case 1:
> @@ -5482,7 +5488,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>               break;
>           case 2:
>               *eax = apicid_pkg_offset(&topo_info);
> -            *ebx = cs->nr_cores * cs->nr_threads;
> +            *ebx = cpus_per_pkg;
>               *ecx |= CPUID_TOPOLOGY_LEVEL_DIE;
>               break;
>           default:
> @@ -5707,7 +5713,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>            * discards multiple thread information if it is set.
>            * So don't set it here for Intel to make Linux guests happy.
>            */
> -        if (cs->nr_cores * cs->nr_threads > 1) {
> +        if (cpus_per_pkg > 1) {
>               if (env->cpuid_vendor1 != CPUID_VENDOR_INTEL_1 ||
>                   env->cpuid_vendor2 != CPUID_VENDOR_INTEL_2 ||
>                   env->cpuid_vendor3 != CPUID_VENDOR_INTEL_3) {
> @@ -5769,7 +5775,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>                *eax |= (cpu_x86_virtual_addr_width(env) << 8);
>           }
>           *ebx = env->features[FEAT_8000_0008_EBX];
> -        if (cs->nr_cores * cs->nr_threads > 1) {
> +        if (cpus_per_pkg > 1) {
>               /*
>                * Bits 15:12 is "The number of bits in the initial
>                * Core::X86::Apic::ApicId[ApicId] value that indicate
> @@ -5777,7 +5783,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>                * Bits 7:0 is "The number of threads in the package is NC+1"
>                */
>               *ecx = (apicid_pkg_offset(&topo_info) << 12) |
> -                   ((cs->nr_cores * cs->nr_threads) - 1);
> +                   (cpus_per_pkg - 1);
>           } else {
>               *ecx = 0;
>           }
Thanks,
Yanan