Re: [PATCH] drm/virtio: share one vbuf cache across all devices

[sashiko-bot@kernel.org]

> virtio_gpu_alloc_vbufs() creates a kmem_cache with the fixed name
> "virtio-gpu-vbufs" for every device and destroys it from
> virtio_gpu_release(), which only runs once the last drm_device
> reference is dropped. If a reference outlives the PCI removal (for
> instance an open /dev/fbN), a rescan probes the device again while the
> old cache still exists:
> 
>   kmem_cache of name 'virtio-gpu-vbufs' already exists
>   WARNING: mm/slab_common.c:111 at __kmem_cache_create_args
>   Call Trace:
>    virtio_gpu_alloc_vbufs
>    virtio_gpu_init
>    virtio_gpu_probe
>    ...
>    pci_rescan_bus
>    rescan_store
> 
> kmem_cache_create() then fails and the new device does not probe.
> 
> The vbuf size is the same for every device, so create the cache once
> at module init and destroy it at module exit instead of per device.
> 
> Reported-by: syzbot+1b129b44597a126d2d79@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1b129b44597a126d2d79
> Fixes: dc5698e80cf7 ("Add virtio gpu driver.")
> Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260926162452.136863-1-ngocthang2710.1999@gmail.com?part=1