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Date: Wed, 2 Dec 2015 14:52:39 +0100
From: Igor Mammedov <imammedo@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 01/10] vl: Don't allow CPU toplogies
 with partially filled cores
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To: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: mdroth@linux.vnet.ibm.com, aik@ozlabs.ru, agraf@suse.de, Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, tyreld@linux.vnet.ibm.com, nfont@linux.vnet.ibm.com, pbonzini@redhat.com, afaerber@suse.de, david@gibson.dropbear.id.au

On Fri, 20 Nov 2015 18:24:30 +0530
Bharata B Rao <bharata@linux.vnet.ibm.com> wrote:

> Prevent guests from booting with CPU topologies that have partially
> filled CPU cores or can result in partially filled CPU cores after
> CPU hotplug like
> 
> -smp 15,sockets=1,cores=4,threads=4,maxcpus=16 or
> -smp 15,sockets=1,cores=4,threads=4,maxcpus=17.

CCing Eduardo who might tell if it's ok wrt x86

> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  vl.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/vl.c b/vl.c
> index 7d993a5..23a1a1e 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1248,6 +1248,15 @@ static void smp_parse(QemuOpts *opts)
>              exit(1);
>          }
>  
> +        if (cpus % threads || max_cpus % threads) {
> +            error_report("cpu topology: "
> +                         "sockets (%u) cores (%u) threads (%u) with "
> +                         "smp_cpus (%u) maxcpus (%u) "
> +                         "will result in partially filled cores",
> +                         sockets, cores, threads, cpus, max_cpus);
> +            exit(1);
> +        }
> +
>          smp_cpus = cpus;
>          smp_cores = cores > 0 ? cores : 1;
>          smp_threads = threads > 0 ? threads : 1;