Re: [PATCH v3 06/17] i386/cpu: Consolidate the use of topo_info in cpu_x86_cpuid()

[Zhao Liu <zhao1.liu@linux.intel.com>]

Hi Babu,

On Wed, Aug 02, 2023 at 11:31:46AM -0500, Moger, Babu wrote:
> Date: Wed, 2 Aug 2023 11:31:46 -0500
> From: "Moger, Babu" <babu.moger@amd.com>
> Subject: Re: [PATCH v3 06/17] i386/cpu: Consolidate the use of topo_info in
>  cpu_x86_cpuid()
> 
> Hi Zhao,
> 
> On 8/1/23 05:35, Zhao Liu wrote:
> > 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
> 
> s/memebers/members/

Thanks! I'll be more careful with my spelling.

-Zhao


> Thanks
> Babu
> 
> > variable "topo_info" should be preferred.
> > 
> > In addition, in cpu_x86_cpuid(), to uniformly use the topology variable,
> > replace env->dies with topo_info.dies_per_pkg as well.
> > 
> > Suggested-by: Robert Hoo <robert.hu@linux.intel.com>
> > Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> > ---
> > Changes since v1:
> >  * Extract cores_per_socket from the code block and use it as a local
> >    variable for cpu_x86_cpuid(). (Yanan)
> >  * Remove vcpus_per_socket variable and use cpus_per_pkg directly.
> >    (Yanan)
> >  * Replace env->dies with topo_info.dies_per_pkg in cpu_x86_cpuid().
> > ---
> >  target/i386/cpu.c | 31 ++++++++++++++++++-------------
> >  1 file changed, 18 insertions(+), 13 deletions(-)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index c80613bfcded..fc50bf98c60e 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -6008,11 +6008,16 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
> >      uint32_t limit;
> >      uint32_t signature[3];
> >      X86CPUTopoInfo topo_info;
> > +    uint32_t cores_per_pkg;
> > +    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;
> >  
> > +    cores_per_pkg = topo_info.cores_per_die * topo_info.dies_per_pkg;
> > +    cpus_per_pkg = cores_per_pkg * topo_info.threads_per_core;
> > +
> >      /* Calculate & apply limits for different index ranges */
> >      if (index >= 0xC0000000) {
> >          limit = env->cpuid_xlevel2;
> > @@ -6048,8 +6053,8 @@ 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) {
> > @@ -6086,8 +6091,8 @@ 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) {
> > +
> > +                if (cores_per_pkg > 1) {
> >                      int addressable_cores_offset =
> >                                                  apicid_pkg_offset(&topo_info) -
> >                                                  apicid_core_offset(&topo_info);
> > @@ -6095,7 +6100,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
> >                      *eax &= ~0xFC000000;
> >                      *eax |= (1 << addressable_cores_offset - 1) << 26;
> >                  }
> > -                if (host_vcpus_per_cache > vcpus_per_socket) {
> > +                if (host_vcpus_per_cache > cpus_per_pkg) {
> >                      int pkg_offset = apicid_pkg_offset(&topo_info);
> >  
> >                      *eax &= ~0x3FFC000;
> > @@ -6240,12 +6245,12 @@ 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;
> >              *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:
> > @@ -6266,7 +6271,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
> >          break;
> >      case 0x1F:
> >          /* V2 Extended Topology Enumeration Leaf */
> > -        if (env->nr_dies < 2) {
> > +        if (topo_info.dies_per_pkg < 2) {
> >              *eax = *ebx = *ecx = *edx = 0;
> >              break;
> >          }
> > @@ -6276,7 +6281,7 @@ 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:
> > @@ -6286,7 +6291,7 @@ 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:
> > @@ -6511,7 +6516,7 @@ 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) {
> > @@ -6577,7 +6582,7 @@ 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
> > @@ -6585,7 +6590,7 @@ 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
> Babu Moger