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

[Hillf Danton <hdanton@sina.com>]

On Sat, 26 Sep 2026 23:24:52 +0700 Nguyen Ngoc Thang wrote:
> 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.
>
What is unclear -- why is kmalloc failing to work in 2026?