AMD General
> -----Original Message-----
> From: Alex Deucher <[email protected]>
> Sent: Friday, September 4, 2026 2:01 AM
> To: Zhang, Jesse(Jie) <[email protected]>
> Cc: [email protected]; Deucher, Alexander
> <[email protected]>; Koenig, Christian <[email protected]>
> Subject: Re: [PATCH V3 08/10] drm/amdgpu/mes_userqueue: route compute
> MODIFY through init_mqd
>
> On Mon, Aug 31, 2026 at 1:50 AM Jesse Zhang <[email protected]> wrote:
> >
> > Set prop->modify and prop->user_wptr (read from the wptr poll BO) and
> > call init_mqd, so a re-enabled compute queue keeps its context-saved
> > rptr and resumes at the first un-consumed packet.
> >
> > Also set modify=false on the create and kernel-ring
> > (amdgpu_ring_to_mqd_prop) paths, so every init_mqd caller states its
> > own value rather than relying on the zeroed prop.
> >
> > v3: set the mqd_prop modify flag and call init_mqd instead of a separate
> > update_mqd callback, per review.
> >
> > Signed-off-by: Jesse Zhang <[email protected]>
> > Suggested-by: Alexander Deucher <[email protected]>
> > ---
> > drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 2 ++
> > drivers/gpu/drm/amd/amdgpu/mes_userqueue.c | 20 +++++++++++++++++++-
> > 2 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
> > index 686c92e96025..9fd0ab0be40e 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
> > @@ -840,6 +840,8 @@ static void amdgpu_ring_to_mqd_prop(struct
> amdgpu_ring *ring,
> > prop->use_doorbell = ring->use_doorbell;
> > prop->doorbell_index = ring->doorbell_index;
> > prop->kernel_queue = true;
> > + /* kernel rings always build the MQD from scratch, never a MODIFY */
> > + prop->modify = false;
> >
> > /* map_queues packet doesn't need activate the queue,
> > * so only kiq need set this field.
> > diff --git a/drivers/gpu/drm/amd/amdgpu/mes_userqueue.c
> > b/drivers/gpu/drm/amd/amdgpu/mes_userqueue.c
> > index 82bb4369451e..c6ac3194e4da 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/mes_userqueue.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/mes_userqueue.c
> > @@ -479,6 +479,7 @@ static int mes_userq_mqd_create(struct
> amdgpu_usermode_queue *queue,
> > userq_props->use_doorbell = true;
> > userq_props->doorbell_index = queue->doorbell_index;
> > userq_props->fence_address = queue->fence_drv->gpu_addr;
> > + userq_props->modify = false;
> >
> > if (queue->queue_type == AMDGPU_HW_IP_COMPUTE) {
> > struct drm_amdgpu_userq_mqd_compute_gfx11
> > *compute_mqd; @@ -681,6 +682,20 @@ static int
> mes_userq_mqd_create(struct amdgpu_usermode_queue *queue,
> > return r;
> > }
> >
> > +/* Read the queue's live user wptr from its poll BO; 0 if not mapped.
> > +*/ static u64 mes_userq_read_user_wptr(struct amdgpu_usermode_queue
> > +*queue) {
> > + u64 user_wptr = 0;
> > + void *wc = NULL;
> > +
> > + if (queue->wptr_obj.obj &&
> > + !amdgpu_bo_kmap(queue->wptr_obj.obj, &wc) && wc) {
> > + user_wptr = *(volatile u64 *)wc;
> > + amdgpu_bo_kunmap(queue->wptr_obj.obj);
> > + }
> > + return user_wptr;
> > +}
>
> Can't we just skip this? The firmware should update the MQD and store the
> current
> rptr/wptr when we unmap it. So when we modify the queue, all we need to do is
> skip any changes to the rptr/wrptr when we modify the MQD. No need to save
> the
> wptr. Other than that, the patches look good to me.
Thanks Alex. You're right, will skip this in v4 - init_mqd just keeps the
firmware context-saved rptr/wptr, dropping the read_user_wptr helper.
Tested all pass.
Jesse
>
> Alex
>
> > +
> > static int mes_userq_compute_mqd_update(struct amdgpu_usermode_queue
> *queue,
> > struct drm_amdgpu_userq_in
> > *args_in) { @@ -707,8 +722,11 @@ static int
> > mes_userq_compute_mqd_update(struct amdgpu_usermode_queue *queue,
> >
> > userq_props->queue_size = args_in->queue_size;
> > userq_props->hqd_base_gpu_addr = args_in->queue_va;
> > + userq_props->modify = true;
> > + userq_props->user_wptr = mes_userq_read_user_wptr(queue);
> >
> > - retval = mqd_hw_default->init_mqd(adev, (void *)queue->mqd.cpu_ptr,
> userq_props);
> > + retval = mqd_hw_default->init_mqd(adev, (void *)queue->mqd.cpu_ptr,
> > + userq_props);
> >
> > free:
> > kfree(compute_mqd_v11);
> > --
> > 2.49.0
> >
