Re: [Qemu-ppc] [PATCH v2] spapr: check smp_threads <= vsmt

[Greg Kurz]

On Thu,  8 Feb 2018 10:42:41 +0100
Laurent Vivier <address@hidden> wrote:

> We ignore silently the value of smp_threads when we set
> the default VSMT value, and if smp_threads is greater than VSMT
> kernel is going into trouble later.
> 
> Fixes: 8904e5a750
> ("spapr: Adjust default VSMT value for better migration compatibility")
> 
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
> 

Reviewed-by: Greg Kurz <address@hidden>

> Notes:
>     v2: display a specific error message when the default VSMT is used
>         fix subject
> 
>  hw/ppc/spapr.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 32a876be56..11de276cd5 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2311,6 +2311,12 @@ static void spapr_set_vsmt_mode(sPAPRMachineState 
> *spapr, Error **errp)
>           * overwhelmingly common case in production systems.
>           */
>          spapr->vsmt = 8;
> +        if (spapr->vsmt < smp_threads) {
> +            error_setg(&local_err, "Cannot support %d threads/core"
> +                         " because it must be <= to default VSMT mode (%d)",
> +                         smp_threads, spapr->vsmt);
> +            goto out;
> +        }
>      }
>  
>      /* KVM: If necessary, set the SMT mode: */