Re: [RFC PATCH 3/6] pc/machine: Perform zero-check for the value of -smp dies

[Andrew Jones]

On Fri, Jul 02, 2021 at 06:07:36PM +0800, Yanan Wang wrote:
> It's possible that dies parameter is explicitly specified as "dies=0"
> in the cmdline, if so we will wrongly calculate the other ommited
> parameters such as "sockets = maxcpus / (dies * cores * threads);"
> with a zeroed dies value.
> 
> So perform zero-check (default the value to 1 if zeroed) for -smp dies
> before using it to calculate other parameters.

OK, dies=0 may make some sense for a user that doesn't want to describe
dies.

Reviewed-by: Andrew Jones <drjones@redhat.com>

> 
> Fixes: 1b45842203540 (vl.c: Add -smp, dies=* command line support and update 
> doc)
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  hw/i386/pc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index a44511c937..93d1f12a49 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -714,12 +714,14 @@ static void pc_smp_parse(MachineState *ms, 
> SMPConfiguration *config, Error **err
>  {
>      unsigned cpus    = config->has_cpus ? config->cpus : 0;
>      unsigned sockets = config->has_sockets ? config->sockets : 0;
> -    unsigned dies    = config->has_dies ? config->dies : 1;
> +    unsigned dies    = config->has_dies ? config->dies : 0;
>      unsigned cores   = config->has_cores ? config->cores : 0;
>      unsigned threads = config->has_threads ? config->threads : 0;
>      unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
>  
>      /* compute missing values, prefer sockets over cores over threads */
> +    dies = dies > 0 ? dies : 1;
> +
>      if (cpus == 0 || sockets == 0) {
>          cores = cores > 0 ? cores : 1;
>          threads = threads > 0 ? threads : 1;
> -- 
> 2.19.1
>