Re: [PATCH v3 0/5] ALSA: virtio: Fix request lifetime and error recovery

[Takashi Iwai <tiwai@suse.de>]

On Tue, 13 Oct 2026 10:57:47 +0200,
Joonho Lee wrote:
> 
> A failed PCM start or a timed-out request can leave virtio-snd messages
> owned by the device after the caller returns. Retrying can then reuse
> pending messages, and freeing ALSA or control buffers can leave their
> addresses in a virtqueue.
> 
> This series fixes enqueue-error recovery and keeps the memory referenced
> by outstanding requests alive until completion or device reset. Reset
> also detaches unused descriptors before deleting the queues, releasing
> their DMA mappings and cancelling PCM messages without reporting them
> as completed audio.
> 
> Changes since v2, following the Sashiko AI review:
> - Patch 2 protects all stopped-state accesses with vss->lock, including
>   hw_params, prepare, open, STOP and sync_stop completion. The RELEASE
>   decision and stopped=true transition now share a critical section.
>   Sleeping operations remain outside the spinlock.
> - Patch 5 aligns every DMA region for both cache maintenance and typed
>   CPU accesses, and removes the initial +1 offset. This handles coherent
>   systems where dma_get_cache_alignment() returns 1, as well as odd
>   region lengths that could otherwise misalign later payloads.
> - Patches 1, 3 and 4 are unchanged.
> 
> Validation of the final v3 source:
> - ARM64 W=1 module build and ARM32 CONFIG_MMU=n driver object build.
> - Source-extracted ASan/UBSan PCM, control, reset, ACK and DMA lifetime
>   regressions on macOS arm64. The v2 control allocator produces UBSan
>   misalignment diagnostics; the v3 allocator passes typed header and
>   request/response integer64 accesses with DMA alignments 1, 2, 4, 8,
>   32, 64 and 128.
> - Deterministic stopped-state lock instrumentation catches unlocked v2
>   accesses and passes 73 lifecycle assertions for v3. It covers ACK
>   failure, RELEASE failure/retry and ACK during RELEASE, and checks that
>   blocking operations do not run with the spinlock held.
> 
> The stopped-state test instruments extracted source; it is not KCSAN or
> an actual threaded kernel race test. NOMMU was compiled, not booted.
> Physical non-coherent DMA hardware and host microphone behavior were
> not tested by these regressions. The QEMU ARM64 KASAN fault/recovery runs
> reported in v2 have not been rerun for these v3 changes.
> 
> Reproducer source and instructions:
> https://github.com/whatisyourname0/virtio-snd-reproducer/tree/3ee5c7c1e864dae50a127b0a25cd122532daa6de
> 
> Based on sound.git for-next commit
> 8d70e364e866bdfca81eee24d0688fac9472cfb9.
> 
> AI assistance was used for code changes, tests, review and patch text.
> Assisted-by trailers are included. Sashiko's findings were checked against
> the driver and covered by regressions before incorporating the fixes.
> 
> Previous series Message-ID:
> <cover.1791877396.git.mynameisjune111@gmail.com>
> 
> Joonho Lee (5):
>   ALSA: virtio: Propagate PCM send failures through ACK
>   ALSA: virtio: Recover PCM state after a failed start
>   ALSA: virtio: Retain queued messages through device reset
>   ALSA: virtio: Keep PCM DMA buffers alive through device ownership
>   ALSA: virtio: Keep control payloads alive through DMA completion

Through a quick glance, the patches look OK, but they are a bit too
heavy changes at this very late stage for the next merge window.
I can take those for 7.4-rc1 if the virtio maintainer gives an ack,
but otherwise postponed for 7.5.

Or, if you have some more urgent fixes to address some known issues,
please cook a smaller patch that can be more easily digested.


thanks,

Takashi