Re: [PATCH v6 07/11] virtio-gpu: Handle resource blob commands

[Pierre-Eric Pelloux-Prayer]

Le 21/12/2023 à 09:09, Akihiko Odaki a écrit :
> On 2023/12/19 16:53, Huang Rui wrote:
> > From: Antonio Caggiano <antonio.caggiano@collabora.com>
> >
> > Support BLOB resources creation, mapping and unmapping by calling the
> > new stable virglrenderer 0.10 interface. Only enabled when available and
> > via the blob config. E.g. -device virtio-vga-gl,blob=true
>
> I have another concern about delaying virgl_renderer_resource_unref() until the 
> resource gets unmapped; the guest will expect the resource ID will be available 
> for a new resource immediately after VIRTIO_GPU_CMD_RESOURCE_UNREF, but it will 
> break the assumption and may corrupt things.

Yes this is a problem.

And another one is virglrenderer is not really thread-safe, so this callstack:

#0  virgl_resource_blob_async_unmap ()
#1  object_finalize ()
#2  object_unref ()
#3  memory_region_unref ()
#4  flatview_destroy ()
#5  call_rcu_thread ()
#6  qemu_thread_start ()

Will call into virgl_renderer_ctx_resource_unmap which in turn uses 
virgl_resource_lookup
without any multithreading considerations.


Regards,
Pierre-Eric