Re: [PATCH v1 4/7] vfio/region: Add a helper to get region index from memory region

["Cédric Le Goater" <clg@redhat.com>]

Hello Vivek,

On 10/4/25 01:35, Vivek Kasireddy wrote:
> Having a way to figure out the region index (or bar) associated
> with a memory region is helpful in various scenarios. For example,
> this capability can be useful in retrieving the region info needed
> for mapping a part of a VFIO region or creating a dmabuf.
> 
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Cédric Le Goater <clg@redhat.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> ---
>   hw/vfio/region.c              | 14 ++++++++++++++
>   include/hw/vfio/vfio-device.h |  2 ++
>   2 files changed, 16 insertions(+)
> 
> diff --git a/hw/vfio/region.c b/hw/vfio/region.c
> index b165ab0b93..8837afc97f 100644
> --- a/hw/vfio/region.c
> +++ b/hw/vfio/region.c
> @@ -398,3 +398,17 @@ void vfio_region_mmaps_set_enabled(VFIORegion *region, bool enabled)
>       trace_vfio_region_mmaps_set_enabled(memory_region_name(region->mem),
>                                           enabled);
>   }
> +
> +int vfio_get_region_index_from_mr(MemoryRegion *mr)
> +{
> +    VFIORegion *region = mr->opaque;
> +
> +    if (mr->ops != &vfio_region_ops) {
> +        mr = mr->container;

May be start the routine with :

     while (mr->container) {
         mr = mr->container;
     }

> +        if (mr->ops != &vfio_region_ops) {
> +            return -1;

I think I would prefer returning a 'VFIORegion *' which should be
NULL in case of error. Looks cleaner.


> +        }
> +	region = mr->opaque;
> +    }
> +    return region->nr;
> +}
> diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
> index 7e9aed6d3c..bdb106c937 100644
> --- a/include/hw/vfio/vfio-device.h
> +++ b/include/hw/vfio/vfio-device.h
> @@ -277,6 +277,8 @@ bool vfio_device_has_region_cap(VFIODevice *vbasedev, int region, uint16_t cap_t
>   
>   int vfio_device_get_irq_info(VFIODevice *vbasedev, int index,
>                                   struct vfio_irq_info *info);
> +
> +int vfio_get_region_index_from_mr(MemoryRegion *mr);
Please add documentation.

Thanks,

C.


>   #endif
>   
>   /* Returns 0 on success, or a negative errno. */