Re: [RFC PATCH v9 3/4] drm/virtio: implement userptr resource support

[sashiko-bot@kernel.org]

> Add userptr blob objects so the guest kernel can pin an existing
> userspace mapping and advertise it as CREATE_BLOB backing entries.
> 
> - New virtio_gpu_object_userptr type for userptr resources
> - Pin pages with pin_user_pages_fast() and FOLL_LONGTERM
> - Omit FOLL_WRITE when VIRTGPU_BLOB_FLAG_USE_READONLY is set
> - Charge FOLL_LONGTERM pins against RLIMIT_MEMLOCK
> - DMA-map the scatterlist only when virtio_gpu_use_dma_api() is
>   required; use DMA_TO_DEVICE for USE_READONLY blobs
> - Mark writable pages dirty when unpinning
> - Keep pages pinned until RESOURCE_UNREF is queued; drop them from
>   cleanup_object() on the unref response or on create failure
> - Clear userptr->pages on pin failure to avoid double-free on cleanup
> - Reject unaligned or overflowing userptr ranges at create time
> - Disallow PRIME export of userptr objects
> - Save CREATE_BLOB params and restore userptr resources after
>   hibernation without using the shmem restore path
> 
> The hibernation restore path maps with the same attrs and direction
> used at create time, as documented next to the call. Like shmem
> blobs, the DMA API can still bounce through a buffer there. This
> design only avoids a second guest side shmem allocation and memcpy,
> nothing more.
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260924095556.1326164-1-honghuan@amd.com?part=3