Re: [PATCH v3 2/3] hw/i386: Add a new check to configure smp dies for EPYC

From: Igor Mammedov <imammedo@redhat.com>
To: Babu Moger <babu.moger@amd.com>
Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, mst@redhat.com,
	ehabkost@redhat.com, rth@twiddle.net
Subject: Re: [PATCH v3 2/3] hw/i386: Add a new check to configure smp dies for EPYC
Date: Fri, 7 Aug 2020 21:27:29 +0200	[thread overview]
Message-ID: <20200807212729.1cb2ede0@redhat.com> (raw)
In-Reply-To: <159681797161.9679.5653247810916709875.stgit@naples-babu.amd.com>

On Fri, 07 Aug 2020 11:32:51 -0500
Babu Moger <babu.moger@amd.com> wrote:

> Adding a new check to warn the users to configure 'dies' when
s/warn .../error out .../

> topology is numa configured. It makes it easy to build the
> topology for EPYC models.

probably it should mention that will break configs that
do not have correct topology configured.

> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>  hw/i386/x86.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index 67bee1bcb8..2a6ce56ef1 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -138,6 +138,13 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
>  
>      /* Check for apicid encoding */
>      if (cpu_x86_use_epyc_apic_id_encoding(ms->cpu_type)) {
> +        if ((ms->numa_state->num_nodes > 0) &&
> +            ms->numa_state->num_nodes != (ms->smp.sockets * x86ms->smp_dies)) {
> +            error_setg(&error_fatal, "Numa configuration requires smp 'dies' "
> +                       "parameter. Configure the cpu topology properly with "
> +                       "max_cpus = sockets * dies * cores * threads");
> +            return;
> +        }
>          x86_set_epyc_topo_handlers(ms);
>      }

we also should error out in case 
    ms->numa_state->num_nodes != (ms->smp.sockets * x86ms->smp_dies
and ask user to configure numa to match total number of used dies.