Re: [PATCH v2 2/3] hw/smbios: Fix thread count in type4

[Igor Mammedov <imammedo@redhat.com>]

On Thu,  1 Jun 2023 17:29:51 +0800
Zhao Liu <zhao1.liu@linux.intel.com> wrote:

> From: Zhao Liu <zhao1.liu@intel.com>
> 
> From SMBIOS 3.0 specification, thread count field means:
> 
> Thread Count is the total number of threads detected by the BIOS for
> this processor socket. It is a processor-wide count, not a
> thread-per-core count. [1]
> 
> So here we should use threads per socket other than threads per core.
> 
> [1] SMBIOS 3.0.0, section 7.5.8, Processor Information - Thread Count
> 
> Fixes: c97294ec1b9e ("SMBIOS: Build aggregate smbios tables and entry point")
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
> Changes since v1:
>  * Rename cpus_per_socket to threads_per_socket.
>  * Add the comment about smp.max_cpus. Thread count and core count will
>    be calculated in 2 ways and will add a sanity check to ensure we
>    don't miss any topology level.
> ---
>  hw/smbios/smbios.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
> index d67415d44dd8..faf82d4ae646 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;
> +    unsigned threads_per_socket;
>  
>      if (smbios_ep_type == SMBIOS_ENTRY_POINT_TYPE_64) {
>          tbl_len = SMBIOS_TYPE_4_LEN_V30;
> @@ -747,17 +748,20 @@ static void smbios_build_type_4_table(MachineState *ms, unsigned instance)
>      SMBIOS_TABLE_SET_STR(4, asset_tag_number_str, type4.asset);
>      SMBIOS_TABLE_SET_STR(4, part_number_str, type4.part);
>  
> +    /* smp.max_cpus is the total number of threads for the system. */
> +    threads_per_socket = ms->smp.max_cpus / ms->smp.sockets;

what I dislike here is introducing topo calculations with its own assumptions
in random places.

I'd suggest to add threads_per_socket (even if it's just a helper field) into
topo structure and calculate it with the rest on topology.
And then use result here.

> +
>      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;
> +    t->thread_count = (threads_per_socket > 255) ? 0xFF : threads_per_socket;
>  
>      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(threads_per_socket);
>      }
>  
>      SMBIOS_BUILD_TABLE_POST;