Claude review: Re: [PATCH v2] drm/virtio: move cursor resv lock acquisition to prepare_fb

[Claude Code Review Bot <claude-review@example.com>]

Overall Series Review

Subject: Re: [PATCH v2] drm/virtio: move cursor resv lock acquisition to prepare_fb
Author: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Patches: 4
Reviewed: 2026-05-16T14:23:37.525668

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This is a single-patch series fixing a real syzbot-reported bug where `virtio_gpu_cursor_plane_update()` ignores the return value of `virtio_gpu_array_lock_resv()`. The unchecked failure leads to `dma_resv_add_fence()` being called without the reservation lock held, causing a lockdep splat and potential fence-list corruption under concurrent access.

The fix correctly moves the fallible resource acquisition (object array allocation, reservation lock, fence slot reservation) from `.atomic_update` — which must not fail per the DRM atomic contract — into `.prepare_fb`, which is the designated callback for fallible resource preparation. This is the standard DRM pattern and the right approach.

The patch is well-structured, the commit message is thorough and explains both the bug mechanism and the design rationale. The lifecycle management (prepare → consume → cleanup) is correct across all paths (success, rollback, cursor-move-without-fb-change).

**Verdict: Good patch, ready to apply with minor observations below.**

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