Re: [PATCH v3 3/4] hw/smbios: Fix thread count in type4

[Zhao Liu]

On Mon, Jun 26, 2023 at 03:44:49PM +0200, Igor Mammedov wrote:
> Date: Mon, 26 Jun 2023 15:44:49 +0200
> From: Igor Mammedov <imammedo@redhat.com>
> Subject: Re: [PATCH v3 3/4] hw/smbios: Fix thread count in type4
> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu)
> 
> On Tue, 20 Jun 2023 18:39:57 +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>
> > ---
> > v3:
> >  * Use the wrapped hepler to get threads per socket.
> > 
> > v2:
> >  * 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 | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
> > index d67415d44dd8..3aae9328c014 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 +748,19 @@ 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);
> >  
> > +    threads_per_socket = machine_topo_get_threads_per_socket(ms);
>                                 ^^^^
> Are there any other places we can clean up and reuse this wrapper?

Yes, in the struct CPUState of include/hw/core/cpu.h, the "nr_cores"
need this helper to wrap the calculation. Also there are scenarios in
the i386 CPUID emulation/MSR_CORE_THREAD_COUNT related things that
require these information.

I have another patchset that contains the related fixes/changes [1].
To avoid conflicts, I thought I would follow up and use our newly
added helper after that patchset has been fully received.

Add WHPX also need cores per socket, but I've used another way to fix
[2].

[1]: https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg07179.html
[2]: https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg07196.html

- Zhao

> 
> > +
> >      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;
>