Re: [PATCH 03/13] drm/xe: Move migrate to prefetch to op_lock_and_prep function

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Apr 18, 2024 at 01:27:13PM -0600, Zeng, Oak wrote:
> 
> 
> > -----Original Message-----
> > From: Brost, Matthew <matthew.brost@intel.com>
> > Sent: Wednesday, April 10, 2024 1:41 AM
> > To: intel-xe@lists.freedesktop.org
> > Cc: Brost, Matthew <matthew.brost@intel.com>; Zeng, Oak
> > <oak.zeng@intel.com>
> > Subject: [PATCH 03/13] drm/xe: Move migrate to prefetch to
> > op_lock_and_prep function
> > 
> > All non-binding operations in VM bind IOCTL should be in the lock and
> > prepare step rather than the execution step. Move prefetch to conform to
> > this pattern.
> > 
> > v2:
> >  - Rebase
> >  - New function names (Oak)
> >  - Update stale comment (Oak)
> > 
> > Cc: Oak Zeng <oak.zeng@intel.com>
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_vm.c | 30 +++++++++++++++---------------
> >  1 file changed, 15 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> > index 84c6b10b4b78..2c0521573154 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.c
> > +++ b/drivers/gpu/drm/xe/xe_vm.c
> > @@ -2039,20 +2039,10 @@ static const u32 region_to_mem_type[] = {
> > 
> >  static struct dma_fence *
> >  xe_vm_prefetch(struct xe_vm *vm, struct xe_vma *vma,
> > -	       struct xe_exec_queue *q, u32 region,
> > -	       struct xe_sync_entry *syncs, u32 num_syncs,
> > -	       bool first_op, bool last_op)
> > +	       struct xe_exec_queue *q, struct xe_sync_entry *syncs,
> > +	       u32 num_syncs, bool first_op, bool last_op)
> 
> 
> I am wondering, do you still need this function? The original prefetch function is migration + vm_bind. Now you moved the migration to lock_and_prepare step, only vm bind left...
> 
> Even if you keep this function, we should change the name... it is not a prefetch anymore...
> 

I'd rather leave as is for the following reasons:

1. The code is slightly different and skip the bind under certain conditions
2. It still implements the prefetch op so name applies
3. This is just a staging patch and this function gets deleted once a
version of [1] is merged, I'd rather not squabble / nit pick code that
is temporary. The goal to not regress behavior while making progress
towards [1].

Matt

[1] https://patchwork.freedesktop.org/patch/582024/?series=125608&rev=5

> Oak
> 
> >  {
> >  	struct xe_exec_queue *wait_exec_queue =
> > to_wait_exec_queue(vm, q);
> > -	int err;
> > -
> > -	xe_assert(vm->xe, region < ARRAY_SIZE(region_to_mem_type));
> > -
> > -	if (!xe_vma_has_no_bo(vma)) {
> > -		err = xe_bo_migrate(xe_vma_bo(vma),
> > region_to_mem_type[region]);
> > -		if (err)
> > -			return ERR_PTR(err);
> > -	}
> > 
> >  	if (vma->tile_mask != (vma->tile_present & ~vma->tile_invalidated))
> > {
> >  		return xe_vm_bind(vm, vma, q, xe_vma_bo(vma), syncs,
> > num_syncs,
> > @@ -2592,8 +2582,7 @@ static struct dma_fence *op_execute(struct xe_vm
> > *vm, struct xe_vma *vma,
> >  				     op->flags & XE_VMA_OP_LAST);
> >  		break;
> >  	case DRM_GPUVA_OP_PREFETCH:
> > -		fence = xe_vm_prefetch(vm, vma, op->q, op-
> > >prefetch.region,
> > -				       op->syncs, op->num_syncs,
> > +		fence = xe_vm_prefetch(vm, vma, op->q, op->syncs, op-
> > >num_syncs,
> >  				       op->flags & XE_VMA_OP_FIRST,
> >  				       op->flags & XE_VMA_OP_LAST);
> >  		break;
> > @@ -2823,9 +2812,20 @@ static int op_lock_and_prep(struct drm_exec
> > *exec, struct xe_vm *vm,
> >  					    false);
> >  		break;
> >  	case DRM_GPUVA_OP_PREFETCH:
> > +	{
> > +		struct xe_vma *vma = gpuva_to_vma(op->base.prefetch.va);
> > +		u32 region = op->prefetch.region;
> > +
> > +		xe_assert(vm->xe, region <=
> > ARRAY_SIZE(region_to_mem_type));
> > +
> >  		err = vma_lock_and_validate(exec,
> > -					    gpuva_to_vma(op-
> > >base.prefetch.va), true);
> > +					    gpuva_to_vma(op-
> > >base.prefetch.va),
> > +					    false);
> > +		if (!err && !xe_vma_has_no_bo(vma))
> > +			err = xe_bo_migrate(xe_vma_bo(vma),
> > +					    region_to_mem_type[region]);
> >  		break;
> > +	}
> >  	default:
> >  		drm_warn(&vm->xe->drm, "NOT POSSIBLE");
> >  	}
> > --
> > 2.34.1
>