[PATCH] virresctrl: Fix updating the mask for a cache resource

[Daniel Henrique Barboza]

On 7/2/21 4:23 AM, Vinayak Kale wrote:
> In 'virResctrlAllocUpdateMask', mask is updated only if 'previous mask' is NULL.
> 
> By default, the bitmask for a cache resource for a VM is initialized with
> 'default-resctrl-group' bitmask. So the 'previous mask' would not be NULL and
> mask won't get updated if cachetune is configured for a VM. This causes libvirt
> to use same bitmask as 'default-resctrl-group' bitmask for a cache resource for
> a VM. This patch fixes the issue.
> 
> Fixes: d8a354954aba9cd45ab0317915a0a2be27c04767
> 
> Signed-off-by: Vinayak Kale <vkale at nvidia.com>
> ---

I was going to suggest whether cachetune couldn't just overwrite the default
mask if it's configured, but that would just shift the problem somewhere else.

This fix seems adequate.

Reviewed-by: Daniel Henrique Barboza <danielhb413 at gmail.com>



>   src/util/virresctrl.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c
> index 35e92022db..a7d36f492c 100644
> --- a/src/util/virresctrl.c
> +++ b/src/util/virresctrl.c
> @@ -1104,8 +1104,10 @@ virResctrlAllocUpdateMask(virResctrlAlloc *alloc,
>           VIR_EXPAND_N(a_type->masks, a_type->nmasks,
>                        cache - a_type->nmasks + 1);
>   
> -    if (!a_type->masks[cache])
> -        a_type->masks[cache] = virBitmapNewCopy(mask);
> +    if (a_type->masks[cache])
> +        virBitmapFree(a_type->masks[cache]);
> +
> +    a_type->masks[cache] = virBitmapNewCopy(mask);
>   
>       return 0;
>   }
>