Re: [PATCH v7 5/5] RDMA/mlx5: get tph for p2p access when registering dma-buf mr

[Michael Gur <michaelgur@nvidia.com>]

On 6/10/2026 10:31 PM, Zhiping Zhang wrote:
> Query dma-buf TPH metadata when registering a dma-buf MR for peer-to-
> peer access to a PCIe endpoint and use it to program requester-side TPH
> on the outbound mkey. If the exporter has no metadata, fall back to the
> existing no-TPH path.
>
> For TPH-backed FRMRs, make the extra ST-table reference belong to the
> hardware mkey handle rather than the transient MR object. Extend the
> FRMR pool API so reuse and final destroy can transfer and drop that ref
> at the handle lifetime boundaries, and add mlx5_st_get_index() to take
> a ref on an already-known ST index.
I'd keep the ST reference tied to MRs, where the ST is actually in use.
There's no functional need to couple ST refcounting to mkey lifetime.
Once an MR is destroyed and its mkey revoked, the mkey can no longer 
generate traffic, it's just an idle entry in the FRMR pool waiting to be 
aged out or reused.
This lets us drop all FRMR pool changes from this patch and keep a 
simple flow of 'acquire on MR create, release on MR destroy'.
> Also decode PH from kernel_vendor_key when recreating pooled mkeys so
> the requester hint matches the pool key.
I've fixed that in a series I've sent earlier this week, please rebase 
next version on top of it.

Thanks,
Michael
> Signed-off-by: Zhiping Zhang <zhipingz@meta.com>
> ---
>   drivers/infiniband/core/frmr_pools.c          |  20 +++-
>   drivers/infiniband/hw/mlx5/mr.c               | 111 +++++++++++++++++-
>   .../net/ethernet/mellanox/mlx5/core/lib/st.c  |  49 ++++++--
>   include/linux/mlx5/driver.h                   |  12 ++
>   include/rdma/frmr_pools.h                     |   5 +-
>   5 files changed, 178 insertions(+), 19 deletions(-)