drm/amdgpu: Resync UALink ring wptr after reboot

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When one side of UALink nodes reboots, its ring wptr resets to 0 while
the peer keeps a stale value. Read the remote wptr and adopt it as the
local wptr and rptr to resync, before the first message is sent. Either
side can notice first, so do this both when setting up the connection
and when receiving the HELLO from the peer.

On the sdma path, read the wptr in a fence callback because the IB buffer
holding the result is recycled once the fence signals, so reading it
after dma_fence_wait_timeout() is too late. The lsdma path copies
synchronously, so it reads the wptr directly.

Take peer->lock in the callers (amdgpu_ualink_remote_interrupt and
amdgpu_ualink_remote_shootdown) instead of in amdgpu_ualink_send_command,
so the ring->ready check and the send are atomic against a concurrent
ring reset.

Move the rptr refresh and ring-full check out of amdgpu_ualink_send_command()
into amdgpu_ualink_ring_check_space(), so it runs under the caller's
peer->lock before the job is allocated.

On a failed NPA-REQ send, reset the connection like the NPA-RSP timeout path
already does, so the next attempt resyncs the ring wptr.

On connection reset, amdgpu_ualink_reset_peer_rings() only clears
ring->ready, so the writeback address is re-registered on the next send.

v10:
  - Fix the resync missed on the receiving side: after a reboot the peer
    may send HELLO before we set up the connection, so resync the ring
    wptr in amdgpu_ualink_process_hello_msg() too.

v9:
  - Fix the unnecessary connection reset after an app exits: the peer is
    idle here but still busy handling NPA revokes on the remote, so the
    HELLO reset a healthy connection. Only send it if the wptr changed.
  - Resync both rings together under peer->lock, read both remote wptr
    before updating either so a failed read changes nothing.

v8:
  - Fix regression with concurrent import ioctls: do the idle check and
    ring reset in amdgpu_ualink_setup_connection() under conn_state->lock,
    and return -EAGAIN for IN_PROGRESS/PENDING first.
  - Reset the peer rings only, the imp/exp xarray cleanup is not needed to
    resync wptr.

v7:
  - With v6 reboot one node of vPOD test passed on minirack.
  - Use the per-remote imported and exported handle lists for the idle
    check instead of walking the xarrays.
  - Rename amdgpu_ualink_resync_peer_rings() to
    amdgpu_ualink_reset_peer_rings(), it only clears ring->ready.

v6:
  - Check idleness per remote accelerator instead of globally, and reset
    the stale connection at the import ioctl so the peer re-runs the
    HELLO handshake after a reboot.

v5:
  - Resync the ring pointers at the import ioctl when the connection is
    completely idle (no exported or imported BOs), so the first command
    from a new application after a remote reboot/reset succeeds.
  - Put the sdma wptr read fence callback on the stack instead of
    allocating it; it is cancelled on timeout so it never outlives the
    call.

v4:
  - Cancel the sdma fence callback on the wait timeout/failure path so it
    cannot write into the caller's stack after the function returns, and
    free the callback state in one place.

v3:
  - Resync both rings at connection setup instead of on the send path.
  - Set the writeback rptr too, the stale value disagrees with the
    resynced wptr until the remote FW writes it back.

v2:
  - Match the FW change: resync wptr only on the first send or after a
    timeout, instead of checking the remote periodically.

Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Mukul Joshi <mukul.joshi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

...

This commit is contained in:

Philip Yang 2026-06-08 22:48:21 -04:00 • committed by Alex Deucher

parent c73391c589

commit 61c057105d

1 changed files with 291 additions and 52 deletions

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drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c

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