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

[Igor Mammedov]

On Thu, 8 Jun 2023 10:51:05 +0800
Zhao Liu <zhao1.liu@intel.com> wrote:

> On Wed, Jun 07, 2023 at 04:49:34PM +0200, Igor Mammedov wrote:
> > Date: Wed, 7 Jun 2023 16:49:34 +0200
> > From: Igor Mammedov <imammedo@redhat.com>
> > Subject: Re: [PATCH v2 2/3] hw/smbios: Fix thread count in type4
> > X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu)
> > 
> > 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.  
> 
> Thanks, I will try this way.

maybe instead a field, a helper function located close to topo code
would be better/more acceptable

> 
> 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;  
> >   
>