diff mbox series

[v9,08/21] i386/cpu: Consolidate the use of topo_info in cpu_x86_cpuid()

Message ID 20240227103231.1556302-9-zhao1.liu@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series Introduce smp.modules for x86 in QEMU | expand

Commit Message

Zhao Liu Feb. 27, 2024, 10:32 a.m. UTC 
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 and 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 members clearly, thus the
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>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
Changes since v8:
 * Add Philippe's reviewed-by tag.

Changes since v7:
 * Renamed cpus_per_pkg to threads_per_pkg. (Xiaoyao)
 * Dropped Michael/Babu's Acked/Tested tags since the code change.
 * Re-added Yongwei's Tested tag For his re-testing.
 * Added Xiaoyao's Reviewed tag.

Changes since v3:
 * Fixed typo. (Babu)

Changes since v1:
 * Extracted cores_per_socket from the code block and use it as a local
   variable for cpu_x86_cpuid(). (Yanan)
 * Removed vcpus_per_socket variable and use cpus_per_pkg directly.
   (Yanan)
 * Replaced env->dies with topo_info.dies_per_pkg in cpu_x86_cpuid().
---
 target/i386/cpu.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

Comments

Xiaoyao Li March 9, 2024, 1:48 p.m. UTC | #1 
On 2/27/2024 6:32 PM, 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 and cs->nr_threads.
> 
> Since the names of cs->nr_cores/cs->nr_threads does not accurately

Again as in v7, please changes to "cs->nr_cores and cs->nr_threads",

"cs->nr_cores/cs->nr_threads" looks like a single variable of division

> represent its meaning, the use of cs->nr_cores/cs->nr_threads is prone
> to confusion and mistakes.
> 
> And the structure X86CPUTopoInfo names its members clearly, thus the
> 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.
Zhao Liu March 10, 2024, 1:44 p.m. UTC | #2 
Hi Xiaoyao,

On Sat, Mar 09, 2024 at 09:48:34PM +0800, Xiaoyao Li wrote:
> Date: Sat, 9 Mar 2024 21:48:34 +0800
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> Subject: Re: [PATCH v9 08/21] i386/cpu: Consolidate the use of topo_info in
>  cpu_x86_cpuid()
> 
> On 2/27/2024 6:32 PM, 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 and cs->nr_threads.
> > 
> > Since the names of cs->nr_cores/cs->nr_threads does not accurately
> 
> Again as in v7, please changes to "cs->nr_cores and cs->nr_threads",
> 
> "cs->nr_cores/cs->nr_threads" looks like a single variable of division
> 

I missed to change this.

Though, TBH, legitimate division operations are going to add spaces
around "/". It's also common practice to represent "or" by "/" w/t
spaces. But I'll change it in the next version to make you happy!

Thanks,
Zhao
diff mbox series

Patch

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index df56c7a449c8..d115fc7002ef 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6017,11 +6017,16 @@  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 threads_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;
+    threads_per_pkg = cores_per_pkg * topo_info.threads_per_core;
+
     /* Calculate & apply limits for different index ranges */
     if (index >= 0xC0000000) {
         limit = env->cpuid_xlevel2;
@@ -6057,8 +6062,8 @@  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 (threads_per_pkg > 1) {
+            *ebx |= threads_per_pkg << 16;
             *edx |= CPUID_HT;
         }
         if (!cpu->enable_pmu) {
@@ -6098,15 +6103,15 @@  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) {
                     addressable_cores_width = apicid_pkg_offset(&topo_info) -
                                               apicid_core_offset(&topo_info);
 
                     *eax &= ~0xFC000000;
                     *eax |= ((1 << addressable_cores_width) - 1) << 26;
                 }
-                if (host_vcpus_per_cache > vcpus_per_socket) {
+                if (host_vcpus_per_cache > threads_per_pkg) {
                     /* Share the cache at package level. */
                     addressable_threads_width = apicid_pkg_offset(&topo_info);
 
@@ -6252,12 +6257,12 @@  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 = threads_per_pkg;
             *ecx |= CPUID_TOPOLOGY_LEVEL_CORE;
             break;
         default:
@@ -6277,7 +6282,7 @@  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;
         }
@@ -6287,7 +6292,7 @@  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:
@@ -6297,7 +6302,7 @@  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 = threads_per_pkg;
             *ecx |= CPUID_TOPOLOGY_LEVEL_DIE;
             break;
         default:
@@ -6525,7 +6530,7 @@  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 (threads_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) {
@@ -6591,7 +6596,7 @@  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 (threads_per_pkg > 1) {
             /*
              * Bits 15:12 is "The number of bits in the initial
              * Core::X86::Apic::ApicId[ApicId] value that indicate
@@ -6599,7 +6604,7 @@  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);
+                   (threads_per_pkg - 1);
         } else {
             *ecx = 0;
         }