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

[Zhao Liu]

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 <zhaotianrui@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 <zhaotianrui@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

> +    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
> 
>