Re: [PATCH] drm/amdgpu: handle pipeline sync without a VM fence

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On Fri, Aug 14, 2026 at 1:35 PM Alex Deucher <[email protected]> wrote:
>
> If we end up emitting a VM fence keep pipeline sync
> associated with that fence.  If not, emit them as
> part of the IB fence.
>
> v2: fix need_pipe_sync handling
>
> Cc: David Rosca <[email protected]>
> Fixes: cb1e657ccac8 ("drm/amdgpu: handle GDS and SPM without a VM fence")
> Signed-off-by: Alex Deucher <[email protected]>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c | 6 +++++-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 8 +++++---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 2 +-
>  3 files changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
> index da4dc489e80bd..360e6f00cb7c0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
> @@ -222,7 +222,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
>                 vm_af = job->hw_vm_fence;
>                 /* VM sequence */
>                 vm_af->ib_wptr = ring->wptr;
> -               amdgpu_vm_flush(ring, job, need_pipe_sync, &emit_spm_needed,
> +               amdgpu_vm_flush(ring, job, &need_pipe_sync, &emit_spm_needed,
>                                 &emit_gds_needed);
>                 vm_af->ib_dw_size =
>                         amdgpu_ring_get_dw_distance(ring, vm_af->ib_wptr, ring->wptr);
> @@ -235,6 +235,10 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
>         if (ring->funcs->insert_start)
>                 ring->funcs->insert_start(ring);
>
> +       /* this may have been handled by amdgpu_vm_flush */
> +       if (need_pipe_sync)
> +               amdgpu_ring_emit_pipeline_sync(ring);
> +
>         if (emit_spm_needed)
>                 adev->gfx.rlc.funcs->update_spm_vmid(adev, ring->xcc_id, ring, job->vmid);
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 71050a86bcc3a..b7d0461184d62 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -772,7 +772,7 @@ bool amdgpu_vm_need_pipeline_sync(struct amdgpu_ring *ring,
>   * Emit a VM flush when it is necessary.
>   */
>  void amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
> -                    bool need_pipe_sync, bool *emit_spm_needed,
> +                    bool *need_pipe_sync, bool *emit_spm_needed,
>                      bool *emit_gds_needed)
>  {
>         struct amdgpu_device *adev = ring->adev;
> @@ -827,7 +827,7 @@ void amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
>         if (gds_switch_needed && emit_fence)
>                 *emit_gds_needed = false;
>
> -       if (!vm_flush_needed && !gds_switch_needed && !need_pipe_sync &&
> +       if (!vm_flush_needed && !gds_switch_needed && !(*need_pipe_sync) &&
>             !cleaner_shader_needed && !spm_update_needed)
>                 return;
>
> @@ -847,8 +847,10 @@ void amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
>                 patch = amdgpu_ring_init_cond_exec(ring,
>                                                    ring->cond_exe_gpu_addr);
>
> -       if (need_pipe_sync)
> +       if (emit_fence && *need_pipe_sync) {
>                 amdgpu_ring_emit_pipeline_sync(ring);
> +               *need_pipe_sync = false;
> +       }
>
>         if (cleaner_shader_needed)
>                 ring->funcs->emit_cleaner_shader(ring);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 7f2ba728e3ed3..d32183cd9e0fc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -512,7 +512,7 @@ int amdgpu_vm_validate(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>                        int (*callback)(void *p, struct amdgpu_bo *bo),
>                        void *param);
>  void amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
> -                    bool need_pipe_sync, bool *emit_spm_needed,
> +                    bool *need_pipe_sync, bool *emit_spm_needed,
>                      bool *emit_gds_needed);
>  int amdgpu_vm_update_pdes(struct amdgpu_device *adev,
>                           struct amdgpu_vm *vm, bool immediate);
> --
> 2.55.0
>