Re: [PATCH] hw/smbios: fix thead count field in type 4 table

[Tianrui Zhao]

在 2023年05月31日 16:42, Zhao Liu 写道:
On Tue, May 30, 2023 at 08:20:34PM +0800, Tianrui Zhao wrote:
Date: Tue, 30 May 2023 20:20:34 +0800
From: Tianrui Zhao <zhaotian...@loongson.cn>
Subject: [PATCH] hw/smbios: fix thead count field in type 4 table
X-Mailer: git-send-email 2.39.1

The thread_count value in smbios type_4 table should be
(ms->smp.cores * ms->smp.threads). As according to smbios spec 7.5
Processor Information (Type 4), the field "Thread Count" means the
"Number of threads per processor socket" rather than number of
threads per core.

When apply this patch, use "-smp 4,sockets=1,cores=2,threads=2" to
boot VM, the dmidecode -t 4 shows like:

Handle 0x0400, DMI type 4, 48 bytes
Processor Information
         Socket Designation: CPU 0
         ...
         Core Count: 2
         Core Enabled: 2
         Thread Count: 4
         Characteristics: None

Signed-off-by: Tianrui Zhao <zhaotian...@loongson.cn>
---
  hw/smbios/smbios.c | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
index d2007e70fb..56aeaa069d 100644
--- a/hw/smbios/smbios.c
+++ b/hw/smbios/smbios.c
@@ -713,6 +713,7 @@ static void smbios_build_type_4_table(MachineState *ms, 
unsigned instance)
  {
      char sock_str[128];
      size_t tbl_len = SMBIOS_TYPE_4_LEN_V28;
+    int count;
  
      if (smbios_ep_type == SMBIOS_ENTRY_POINT_TYPE_64) {
          tbl_len = SMBIOS_TYPE_4_LEN_V30;
@@ -749,15 +750,15 @@ static void smbios_build_type_4_table(MachineState *ms, 
unsigned instance)
  
      t->core_count = (ms->smp.cores > 255) ? 0xFF : ms->smp.cores;
      t->core_enabled = t->core_count;
-
-    t->thread_count = (ms->smp.threads > 255) ? 0xFF : ms->smp.threads;
+    count = ms->smp.cores * ms->smp.threads;
Hi Ani & Tianrui,

 From the comment of CpuTopology (include/hw/boards.h):

ms->cores means the "the number of cores in one cluster".
ms->threads means the "the number of threads in one core".

So ms->cores * ms->threads means the number of threads in one cluster
not one socket.

That's why I count the number of threads in a socket by "ms->smp.max_cpus
/ ms->smp.sockets" in [1].

The other correct way is:
ms->smp.cluster * ms->smp.cores * ms->smp.threads.

[1]: https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg07229.html

Thanks,
Zhao
Thanks for your explanations for  the meaning of the number of threads 
per socket, I look up the relevant code again and I agree with your 
patch [1].

Thanks
Tianrui Zhao
+    t->thread_count = (count > 255) ? 0xFF : count;
  
      t->processor_characteristics = cpu_to_le16(0x02); /* Unknown */
      t->processor_family2 = cpu_to_le16(0x01); /* Other */
  
      if (tbl_len == SMBIOS_TYPE_4_LEN_V30) {
          t->core_count2 = t->core_enabled2 = cpu_to_le16(ms->smp.cores);
-        t->thread_count2 = cpu_to_le16(ms->smp.threads);
+        t->thread_count2 = cpu_to_le16(count);
      }
  
      SMBIOS_BUILD_TABLE_POST;
--
2.39.1