| Message ID | 20250109005553.623947-1-airlied@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | nouveau/fence: handle cross device fences properly. (v3) | expand |
On 9/1/25 10:55, Dave Airlie wrote: > From: Dave Airlie <airlied@redhat.com> > > This is the 3rd iteration of this after talking to Ben and > Danilo, I think this makes sense now. > > The fence sync logic doesn't handle a fence sync across devices > as it tries to write to a channel offset from one device into > the fence bo from a different device, which won't work so well. > > This patch fixes that to avoid using the sync path in the case > where the fences come from different nouveau drm devices. > > This works fine on a single device as the fence bo is shared > across the devices, and mapped into each channels vma space, > the channel offsets are therefore okay to pass between sides, > so one channel can sync on the seqnos from the other by using > the offset into it's vma. > > Signed-off-by: Dave Airlie <airlied@redhat.com> Signed-off-by: Ben Skeggs <bskeggs@nvidia.com> > Cc: stable@vger.kernel.org > --- > drivers/gpu/drm/nouveau/nouveau_fence.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c > index ee5e9d40c166..a3eb1f447a29 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_fence.c > +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c > @@ -367,11 +367,13 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, > if (f) { > struct nouveau_channel *prev; > bool must_wait = true; > + bool local; > > rcu_read_lock(); > prev = rcu_dereference(f->channel); > - if (prev && (prev == chan || > - fctx->sync(f, prev, chan) == 0)) > + local = prev && prev->drm == chan->drm; > + if (local && (prev == chan || > + fctx->sync(f, prev, chan) == 0)) > must_wait = false; > rcu_read_unlock(); > if (!must_wait)
On 9/1/25 13:42, Ben Skeggs wrote: > On 9/1/25 10:55, Dave Airlie wrote: > >> From: Dave Airlie <airlied@redhat.com> >> >> This is the 3rd iteration of this after talking to Ben and >> Danilo, I think this makes sense now. >> >> The fence sync logic doesn't handle a fence sync across devices >> as it tries to write to a channel offset from one device into >> the fence bo from a different device, which won't work so well. >> >> This patch fixes that to avoid using the sync path in the case >> where the fences come from different nouveau drm devices. >> >> This works fine on a single device as the fence bo is shared >> across the devices, and mapped into each channels vma space, >> the channel offsets are therefore okay to pass between sides, >> so one channel can sync on the seqnos from the other by using >> the offset into it's vma. >> >> Signed-off-by: Dave Airlie <airlied@redhat.com> > Signed-off-by: Ben Skeggs <bskeggs@nvidia.com> Err, not sure what my fingers did there ;) Reviewed-by: Ben Skeggs <bskeggs@nvidia.com> > >> Cc: stable@vger.kernel.org >> --- >> drivers/gpu/drm/nouveau/nouveau_fence.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c >> b/drivers/gpu/drm/nouveau/nouveau_fence.c >> index ee5e9d40c166..a3eb1f447a29 100644 >> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c >> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c >> @@ -367,11 +367,13 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, >> struct nouveau_channel *chan, >> if (f) { >> struct nouveau_channel *prev; >> bool must_wait = true; >> + bool local; >> rcu_read_lock(); >> prev = rcu_dereference(f->channel); >> - if (prev && (prev == chan || >> - fctx->sync(f, prev, chan) == 0)) >> + local = prev && prev->drm == chan->drm; >> + if (local && (prev == chan || >> + fctx->sync(f, prev, chan) == 0)) >> must_wait = false; >> rcu_read_unlock(); >> if (!must_wait)
On Thu, Jan 09, 2025 at 10:55:53AM +1000, Dave Airlie wrote: > From: Dave Airlie <airlied@redhat.com> > > This is the 3rd iteration of this after talking to Ben and > Danilo, I think this makes sense now. > > The fence sync logic doesn't handle a fence sync across devices > as it tries to write to a channel offset from one device into > the fence bo from a different device, which won't work so well. > > This patch fixes that to avoid using the sync path in the case > where the fences come from different nouveau drm devices. > > This works fine on a single device as the fence bo is shared > across the devices, and mapped into each channels vma space, > the channel offsets are therefore okay to pass between sides, > so one channel can sync on the seqnos from the other by using > the offset into it's vma. Huh, they indeed all share and map drm->fence->bo, good catch. > > Signed-off-by: Dave Airlie <airlied@redhat.com> > Cc: stable@vger.kernel.org > --- > drivers/gpu/drm/nouveau/nouveau_fence.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c > index ee5e9d40c166..a3eb1f447a29 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_fence.c > +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c > @@ -367,11 +367,13 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, > if (f) { > struct nouveau_channel *prev; > bool must_wait = true; > + bool local; > > rcu_read_lock(); > prev = rcu_dereference(f->channel); > - if (prev && (prev == chan || > - fctx->sync(f, prev, chan) == 0)) > + local = prev && prev->drm == chan->drm; struct nouveau_channel has no pointer to a struct nouveau_drm, this should be prev->cli->drm and chan->cli->drm instead. No need to resend, I can fix it when applying the patch if you want. > + if (local && (prev == chan || > + fctx->sync(f, prev, chan) == 0)) > must_wait = false; > rcu_read_unlock(); > if (!must_wait) > -- > 2.43.0 >
diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c index ee5e9d40c166..a3eb1f447a29 100644 --- a/drivers/gpu/drm/nouveau/nouveau_fence.c +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c @@ -367,11 +367,13 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, if (f) { struct nouveau_channel *prev; bool must_wait = true; + bool local; rcu_read_lock(); prev = rcu_dereference(f->channel); - if (prev && (prev == chan || - fctx->sync(f, prev, chan) == 0)) + local = prev && prev->drm == chan->drm; + if (local && (prev == chan || + fctx->sync(f, prev, chan) == 0)) must_wait = false; rcu_read_unlock(); if (!must_wait)