Re: [PATCH v2] virtio_balloon: disable indirect descriptors

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/5/26 08:24, Michael S. Tsirkin wrote:
> The page reporting callback submits an sg list to the reporting
> virtqueue.  With VIRTIO_RING_F_INDIRECT_DESC negotiated and
> total_sg > 1 (which it typically is), virtqueue_add reports it to the
> host by allocating an indirect descriptor via kmalloc(GFP_KERNEL).
> 
> This is not pretty: the reporting worker isolates potentially hundreds
> of MB of free pages from the buddy allocator (reported pages are at
> least pageblock_order, and the sg can contain up to
> PAGE_REPORTING_CAPACITY entries of varying orders).  As the result,
> very theoretically, the kmalloc might trigger OOM when we have in fact a
> ton of free memory.
> 
> Clear VIRTIO_RING_F_INDIRECT_DESC, to avoid using indirect descriptors.
> 
> Fixes: b0c504f15471 ("virtio-balloon: add support for providing free page reports to host")
> Assisted-by: Claude:claude-opus-4-6
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> 
> I assume I'm the one merging this?
> 

I would think so :)

-- 
Cheers,

David