Re: [PATCH v13 4/5] vfio/pci: implement get_pci_tph and DMA_BUF_TPH feature

> Implement dma-buf get_pci_tph for vfio-pci exported dma-bufs and add
> VFIO_DEVICE_FEATURE_DMA_BUF_TPH so userspace can publish TPH metadata
> for a VFIO-owned device.
> 
> 8-bit ST and 16-bit Extended ST are distinct PCIe TPH namespaces; the
> uAPI carries both with explicit validity flags, and get_pci_tph()
> returns the value matching the importer's requested namespace or
> -EOPNOTSUPP.
> 
> Publish and read the TPH descriptor under dmabuf->resv, matching the
> locking used for other importer-visible dma-buf state. The SET ioctl
> takes dma_resv_lock_interruptible(), while the callback runs under
> DMA-buf's asserted resv lock.
> 
> Hold memory_lock in the SET path while checking that the dma-buf still
> [ ... ]
> supported on a device that advertises TPH Completer support but cannot
> export a vfio dma-buf at all, so no dma-buf can ever exist to carry the
> metadata and every SET would fail later at the ownership check.
> 
> Signed-off-by: Zhiping Zhang <[email protected]>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4