[Intel-xe] [PATCH v2 28/31] drm/xe: Allow dma-fences as in-syncs for compute / faulting VM

[Matthew Brost]

On Fri, May 05, 2023 at 03:43:15PM -0400, Rodrigo Vivi wrote:
> On Mon, May 01, 2023 at 05:17:24PM -0700, Matthew Brost wrote:
> > This is allowed per the dma-fencing rules.
> 
> it would be good a word saying 'why' we are doing this.
> only because we can it doesn't mean we should...
> 

This is allowed and encouraged the dma-fencing rule. This along with
allowing compute VMs to export dma-fences on binds will result in a
simpler compute UMD.

Sound ok?

Matt
  
> > 
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_sync.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c
> > index 99f1ed87196d..1e4e4acb2c4a 100644
> > --- a/drivers/gpu/drm/xe/xe_sync.c
> > +++ b/drivers/gpu/drm/xe/xe_sync.c
> > @@ -105,6 +105,7 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  {
> >  	struct drm_xe_sync sync_in;
> >  	int err;
> > +	bool signal;
> >  
> >  	if (copy_from_user(&sync_in, sync_user, sizeof(*sync_user)))
> >  		return -EFAULT;
> > @@ -113,9 +114,10 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  			 ~(SYNC_FLAGS_TYPE_MASK | DRM_XE_SYNC_SIGNAL)))
> >  		return -EINVAL;
> >  
> > +	signal = sync_in.flags & DRM_XE_SYNC_SIGNAL;
> >  	switch (sync_in.flags & SYNC_FLAGS_TYPE_MASK) {
> >  	case DRM_XE_SYNC_SYNCOBJ:
> > -		if (XE_IOCTL_ERR(xe, no_dma_fences))
> > +		if (XE_IOCTL_ERR(xe, no_dma_fences && signal))
> >  			return -ENOTSUPP;
> >  
> >  		if (XE_IOCTL_ERR(xe, upper_32_bits(sync_in.addr)))
> > @@ -125,7 +127,7 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  		if (XE_IOCTL_ERR(xe, !sync->syncobj))
> >  			return -ENOENT;
> >  
> > -		if (!(sync_in.flags & DRM_XE_SYNC_SIGNAL)) {
> > +		if (!signal) {
> >  			sync->fence = drm_syncobj_fence_get(sync->syncobj);
> >  			if (XE_IOCTL_ERR(xe, !sync->fence))
> >  				return -EINVAL;
> > @@ -133,7 +135,7 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  		break;
> >  
> >  	case DRM_XE_SYNC_TIMELINE_SYNCOBJ:
> > -		if (XE_IOCTL_ERR(xe, no_dma_fences))
> > +		if (XE_IOCTL_ERR(xe, no_dma_fences && signal))
> >  			return -ENOTSUPP;
> >  
> >  		if (XE_IOCTL_ERR(xe, upper_32_bits(sync_in.addr)))
> > @@ -146,7 +148,7 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  		if (XE_IOCTL_ERR(xe, !sync->syncobj))
> >  			return -ENOENT;
> >  
> > -		if (sync_in.flags & DRM_XE_SYNC_SIGNAL) {
> > +		if (signal) {
> >  			sync->chain_fence = dma_fence_chain_alloc();
> >  			if (!sync->chain_fence)
> >  				return -ENOMEM;
> > @@ -168,7 +170,7 @@ int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> >  		break;
> >  
> >  	case DRM_XE_SYNC_USER_FENCE:
> > -		if (XE_IOCTL_ERR(xe, !(sync_in.flags & DRM_XE_SYNC_SIGNAL)))
> > +		if (XE_IOCTL_ERR(xe, !signal))
> >  			return -ENOTSUPP;
> >  
> >  		if (XE_IOCTL_ERR(xe, sync_in.addr & 0x7))
> > -- 
> > 2.34.1
> >