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Date: Tue, 18 Aug 2015 16:39:10 -0700
From: Thomas Huth <thuth@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] Add another sanity check to smp_parse()
 function
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To: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-trivial@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>

On 22/07/15 06:59, Thomas Huth wrote:
> The code in smp_parse already checks the topology information for
> sockets * cores * threads < cpus and bails out with an error in
> that case. However, it is still possible to supply a bad configuration
> the other way round, e.g. with:
> 
>  qemu-system-xxx -smp 4,sockets=1,cores=4,threads=2
> 
> QEMU then still starts the guest, with topology configuration that
> is rather incomprehensible and likely not what the user wanted.
> So let's add another check to refuse such wrong configurations.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  vl.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/vl.c b/vl.c
> index 5856396..c8d24b1 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1224,7 +1224,13 @@ static void smp_parse(QemuOpts *opts)
>              exit(1);
>          }
>  
> -        max_cpus = qemu_opt_get_number(opts, "maxcpus", 0);
> +        max_cpus = qemu_opt_get_number(opts, "maxcpus", cpus);
> +        if (sockets * cores * threads > max_cpus) {
> +            fprintf(stderr, "cpu topology: error: "
> +                    "sockets (%u) * cores (%u) * threads (%u) > maxcpus (%u)\n",
> +                    sockets, cores, threads, max_cpus);
> +            exit(1);
> +        }
>  
>          smp_cpus = cpus;
>          smp_cores = cores > 0 ? cores : 1;

*ping*

 Thomas