Re: [PATCH v11 0/4] vfio/dma-buf: add TPH support for peer-to-peer access

[Alex Williamson <alex@shazbot.org>]

On Thu, 2 Jul 2026 11:10:13 -0700
Zhiping Zhang <zhipingz@meta.com> wrote:
 
> Changes since v10:
>   Patch 2 (dma-buf): Per Christian König, document that the ST/PH
>   returned by dma_buf_get_pci_tph() is only valid until the exporter
>   invalidates the current mapping and must be re-queried afterwards;
>   note added to the wrapper kernel-doc and referenced from the callback
>   kernel-doc. Also add dma_buf_get_pci_tph() and dma_buf_ops.get_pci_tph()
>   to the central dma-buf locking convention.
> 
>   Patch 3 (vfio/pci): Per Alex Williamson, update the vfio_pci_dma_buf
>   comment to note that @revoked is additionally protected by memory_lock,
>   and describe the READ_ONCE() rationale in the commit log. No behavior
>   change.

Sashiko has valid comments[1] across most of the series.

 - Passing through 0b10 seems mis-categorized as High in patch 1, but
   is valid hardening if tph_req_type can ever hold an invalid value.

 - The documentation error in patch 2 is real.

 - Patch 4 ironically fails to re-validate according to the lifecycle
   requirements that patch 2 specifies.  This is a significant gap in
   the implementation proof for a real requester.

 - The broadened scope of the existing memory leak in patch 4 is
   already addressed in [2], ok.  Maybe should be folded into this
   series if mlx5 isn't going to pick it up separately.

Thanks,
Alex

[1]https://sashiko.dev/#/patchset/20260702181025.2694961-1-zhipingz@meta.com
[2]https://lore.kernel.org/linux-rdma/20260612170406.3339093-1-zhipingz@meta.com