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

[Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>]

On Sun, 27 Sep 2026, Hillf Danton wrote:
> What is unclear -- why is kmalloc failing to work in 2026?

kmalloc isn't failing. The failure is in kmem_cache_create(): the driver
creates a dedicated cache with a fixed global name for each device, so a
second probe while the first drm_device is still alive (release is
deferred by an open /dev/fbN) trips the duplicate-name check.

Your question made me look at whether the dedicated cache is needed at all.
A vbuf is sizeof(struct virtio_gpu_vbuffer) + 96 + 24 = 216 bytes, which
lands in kmalloc-256 anyway, so the cache buys nothing over kzalloc()/kfree().
Dropping it also removes the lifetime problem entirely and needs no
module-level state.

I'll send a v2 that switches the kmem_cache_zalloc() calls and
kmem_cache_free() to kzalloc()/kfree() and deletes the cache setup and
teardown.

Thanks,
Nguyen Ngoc Thang