Re: [Intel-gfx] [PATCH 15/15] RFC: drm/amdgpu: Implement a proper implicit fencing uapi

Daniel Vetter
2021-06-23T15:12:19Z

On Wed, Jun 23, 2021 at 05:07:17PM +0200, Christian König wrote:
> Am 23.06.21 um 17:03 schrieb Daniel Vetter:
> > On Wed, Jun 23, 2021 at 04:58:27PM +0200, Bas Nieuwenhuizen wrote:
> > > On Wed, Jun 23, 2021 at 4:50 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > On Wed, Jun 23, 2021 at 4:02 PM Christian König
> > > > <christian.koenig@amd.com> wrote:
> > > > > Am 23.06.21 um 15:49 schrieb Daniel Vetter:
> > > > > > On Wed, Jun 23, 2021 at 3:44 PM Christian König
> > > > > > <christian.koenig@amd.com> wrote:
> > > > > > > Am 23.06.21 um 15:38 schrieb Bas Nieuwenhuizen:
> > > > > > > > On Wed, Jun 23, 2021 at 2:59 PM Christian König
> > > > > > > > <christian.koenig@amd.com> wrote:
> > > > > > > > > Am 23.06.21 um 14:18 schrieb Daniel Vetter:
> > > > > > > > > > On Wed, Jun 23, 2021 at 11:45 AM Bas Nieuwenhuizen
> > > > > > > > > > <bas@basnieuwenhuizen.nl> wrote:
> > > > > > > > > > > On Tue, Jun 22, 2021 at 6:55 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > > > > > > > > > WARNING: Absolutely untested beyond "gcc isn't dying in agony".
> > > > > > > > > > > >
> > > > > > > > > > > > Implicit fencing done properly needs to treat the implicit fencing
> > > > > > > > > > > > slots like a funny kind of IPC mailbox. In other words it needs to be
> > > > > > > > > > > > explicitly. This is the only way it will mesh well with explicit
> > > > > > > > > > > > fencing userspace like vk, and it's also the bare minimum required to
> > > > > > > > > > > > be able to manage anything else that wants to use the same buffer on
> > > > > > > > > > > > multiple engines in parallel, and still be able to share it through
> > > > > > > > > > > > implicit sync.
> > > > > > > > > > > >
> > > > > > > > > > > > amdgpu completely lacks such an uapi. Fix this.
> > > > > > > > > > > >
> > > > > > > > > > > > Luckily the concept of ignoring implicit fences exists already, and
> > > > > > > > > > > > takes care of all the complexities of making sure that non-optional
> > > > > > > > > > > > fences (like bo moves) are not ignored. This support was added in
> > > > > > > > > > > >
> > > > > > > > > > > > commit 177ae09b5d699a5ebd1cafcee78889db968abf54
> > > > > > > > > > > > Author: Andres Rodriguez <andresx7@gmail.com>
> > > > > > > > > > > > Date: Fri Sep 15 20:44:06 2017 -0400
> > > > > > > > > > > >
> > > > > > > > > > > > drm/amdgpu: introduce AMDGPU_GEM_CREATE_EXPLICIT_SYNC v2
> > > > > > > > > > > >
> > > > > > > > > > > > Unfortuantely it's the wrong semantics, because it's a bo flag and
> > > > > > > > > > > > disables implicit sync on an allocated buffer completely.
> > > > > > > > > > > >
> > > > > > > > > > > > We _do_ want implicit sync, but control it explicitly. For this we
> > > > > > > > > > > > need a flag on the drm_file, so that a given userspace (like vulkan)
> > > > > > > > > > > > can manage the implicit sync slots explicitly. The other side of the
> > > > > > > > > > > > pipeline (compositor, other process or just different stage in a media
> > > > > > > > > > > > pipeline in the same process) can then either do the same, or fully
> > > > > > > > > > > > participate in the implicit sync as implemented by the kernel by
> > > > > > > > > > > > default.
> > > > > > > > > > > >
> > > > > > > > > > > > By building on the existing flag for buffers we avoid any issues with
> > > > > > > > > > > > opening up additional security concerns - anything this new flag here
> > > > > > > > > > > > allows is already.
> > > > > > > > > > > >
> > > > > > > > > > > > All drivers which supports this concept of a userspace-specific
> > > > > > > > > > > > opt-out of implicit sync have a flag in their CS ioctl, but in reality
> > > > > > > > > > > > that turned out to be a bit too inflexible. See the discussion below,
> > > > > > > > > > > > let's try to do a bit better for amdgpu.
> > > > > > > > > > > >
> > > > > > > > > > > > This alone only allows us to completely avoid any stalls due to
> > > > > > > > > > > > implicit sync, it does not yet allow us to use implicit sync as a
> > > > > > > > > > > > strange form of IPC for sync_file.
> > > > > > > > > > > >
> > > > > > > > > > > > For that we need two more pieces:
> > > > > > > > > > > >
> > > > > > > > > > > > - a way to get the current implicit sync fences out of a buffer. Could
> > > > > > > > > > > > be done in a driver ioctl, but everyone needs this, and generally a
> > > > > > > > > > > > dma-buf is involved anyway to establish the sharing. So an ioctl on
> > > > > > > > > > > > the dma-buf makes a ton more sense:
> > > > > > > > > > > >
> > > > > > > > > > > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2F20210520190007.534046-4-jason%40jlekstrand.net%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C517f0d3467324e7ce05008d936581f60%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637600574408265873%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=gntXLzlrqPxYj4Q3mQflD3arT9ad40S9AqsvtOXV4nk%3D&amp;reserved=0
> > > > > > > > > > > >
> > > > > > > > > > > > Current drivers in upstream solves this by having the opt-out flag
> > > > > > > > > > > > on their CS ioctl. This has the downside that very often the CS
> > > > > > > > > > > > which must actually stall for the implicit fence is run a while
> > > > > > > > > > > > after the implicit fence point was logically sampled per the api
> > > > > > > > > > > > spec (vk passes an explicit syncobj around for that afaiui), and so
> > > > > > > > > > > > results in oversync. Converting the implicit sync fences into a
> > > > > > > > > > > > snap-shot sync_file is actually accurate.
> > > > > > > > > > > >
> > > > > > > > > > > > - Simillar we need to be able to set the exclusive implicit fence.
> > > > > > > > > > > > Current drivers again do this with a CS ioctl flag, with again the
> > > > > > > > > > > > same problems that the time the CS happens additional dependencies
> > > > > > > > > > > > have been added. An explicit ioctl to only insert a sync_file (while
> > > > > > > > > > > > respecting the rules for how exclusive and shared fence slots must
> > > > > > > > > > > > be update in struct dma_resv) is much better. This is proposed here:
> > > > > > > > > > > >
> > > > > > > > > > > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2F20210520190007.534046-5-jason%40jlekstrand.net%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C517f0d3467324e7ce05008d936581f60%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637600574408265873%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=YtqHT756jlt5NX7Ydr3Kk1UMTb98nQhlcOlrnr%2B48HE%3D&amp;reserved=0
> > > > > > > > > > > >
> > > > > > > > > > > > These three pieces together allow userspace to fully control implicit
> > > > > > > > > > > > fencing and remove all unecessary stall points due to them.
> > > > > > > > > > > >
> > > > > > > > > > > > Well, as much as the implicit fencing model fundamentally allows:
> > > > > > > > > > > > There is only one set of fences, you can only choose to sync against
> > > > > > > > > > > > only writers (exclusive slot), or everyone. Hence suballocating
> > > > > > > > > > > > multiple buffers or anything else like this is fundamentally not
> > > > > > > > > > > > possible, and can only be fixed by a proper explicit fencing model.
> > > > > > > > > > > >
> > > > > > > > > > > > Aside from that caveat this model gets implicit fencing as closely to
> > > > > > > > > > > > explicit fencing semantics as possible:
> > > > > > > > > > > >
> > > > > > > > > > > > On the actual implementation I opted for a simple setparam ioctl, no
> > > > > > > > > > > > locking (just atomic reads/writes) for simplicity. There is a nice
> > > > > > > > > > > > flag parameter in the VM ioctl which we could use, except:
> > > > > > > > > > > > - it's not checked, so userspace likely passes garbage
> > > > > > > > > > > > - there's already a comment that userspace _does_ pass garbage in the
> > > > > > > > > > > > priority field
> > > > > > > > > > > > So yeah unfortunately this flag parameter for setting vm flags is
> > > > > > > > > > > > useless, and we need to hack up a new one.
> > > > > > > > > > > >
> > > > > > > > > > > > v2: Explain why a new SETPARAM (Jason)
> > > > > > > > > > > >
> > > > > > > > > > > > v3: Bas noticed I forgot to hook up the dependency-side shortcut. We
> > > > > > > > > > > > need both, or this doesn't do much.
> > > > > > > > > > > >
> > > > > > > > > > > > v4: Rebase over the amdgpu patch to always set the implicit sync
> > > > > > > > > > > > fences.
> > > > > > > > > > > So I think there is still a case missing in this implementation.
> > > > > > > > > > > Consider these 3 cases
> > > > > > > > > > >
> > > > > > > > > > > (format: a->b: b waits on a. Yes, I know arrows are hard)
> > > > > > > > > > >
> > > > > > > > > > > explicit->explicit: This doesn't wait now, which is good
> > > > > > > > > > > Implicit->explicit: This doesn't wait now, which is good
> > > > > > > > > > > explicit->implicit : This still waits as the explicit submission still
> > > > > > > > > > > adds shared fences and most things that set an exclusive fence for
> > > > > > > > > > > implicit sync will hence wait on it.
> > > > > > > > > > >
> > > > > > > > > > > This is probably good enough for what radv needs now but also sounds
> > > > > > > > > > > like a risk wrt baking in new uapi behavior that we don't want to be
> > > > > > > > > > > the end result.
> > > > > > > > > > >
> > > > > > > > > > > Within AMDGPU this is probably solvable in two ways:
> > > > > > > > > > >
> > > > > > > > > > > 1) Downgrade AMDGPU_SYNC_NE_OWNER to AMDGPU_SYNC_EXPLICIT for shared fences.
> > > > > > > > > > I'm not sure that works. I think the right fix is that radeonsi also
> > > > > > > > > > switches to this model, with maybe a per-bo CS flag to set indicate
> > > > > > > > > > write access, to cut down on the number of ioctls that are needed
> > > > > > > > > > otherwise on shared buffers. This per-bo flag would essentially select
> > > > > > > > > > between SYNC_NE_OWNER and SYNC_EXPLICIT on a per-buffer basis.
> > > > > > > > > Yeah, but I'm still not entirely sure why that approach isn't sufficient?
> > > > > > > > >
> > > > > > > > > Problem with the per context or per vm flag is that you then don't get
> > > > > > > > > any implicit synchronization any more when another process starts using
> > > > > > > > > the buffer.
> > > > > > > > That is exactly what I want for Vulkan :)
> > > > > > > Yeah, but as far as I know this is not something we can do.
> > > > > > >
> > > > > > > See we have use cases like screen capture and debug which rely on that
> > > > > > > behavior.
> > > > > > They will keep working, if (and only if) the vulkan side sets the
> > > > > > winsys fences correctly. Also, everything else in vulkan aside from
> > > > > > winsys is explicitly not synced at all, you have to import drm syncobj
> > > > > > timeline on the gl side.
> > > > > >
> > > > > > > The only thing we can do is to say on a per buffer flag that a buffer
> > > > > > > should not participate in implicit sync at all.
> > > > > > Nah, this doesn't work. Because it's not a global decision, is a local
> > > > > > decision for the rendered. Vulkan wants to control implicit sync
> > > > > > explicitly, and the kernel can't force more synchronization. If a
> > > > > > buffer is shared as a winsys buffer between vulkan client and gl using
> > > > > > compositor, then you _have_ to use implicit sync on it. But vk needs
> > > > > > to set the fences directly (and if the app gets it wrong, you get
> > > > > > misrendering, but that is the specified behavour of vulkan).
> > > > > Yeah, but that's exactly what we tried to avoid.
> > > > >
> > > > > Mhm, when we attach the flag to the process/VM then this would break the
> > > > > use case of VA-API and Vulkan in the same process.
> > > > >
> > > > > But I think if you attach the flag to the context that should indeed
> > > > > work fine.
> > > > Yeah that's a question I have, whether the drm_file is shared within
> > > > one process among everything, or whether radeonsi/libva/vk each have
> > > > their own. If each have their own drm_file, then we should be fine,
> > > > otherwise we need to figure out another place to put this (worst case
> > > > as a CS extension that vk just sets on every submit).
> > > libdrm_amdgpu dedupes it all so we mostly end up with one drm_file per
> > > process (modulo minigbm on chromeos and modulo a master fd).
> > >
> > > That said the current proposal is for the context right? And on the
> > > context this should pretty much work? So I'm not sure why this is the
> > > part we are discussing?
> > It's on the fpriv->vm, so on the FD. I assumed vulkan at least would want
> > to have it's private VM for this. And on the quick I didn't see any other
> > way to create a VM than to have an FD of your own.
>
> You can't have your own FD in libdrm_amdgpu userspace. We had a pretty hard
> design discussion about that already.
>
> What you could do is to load your own copy of libdrm_amdgpu, but I won't
> recommend that.
>
> Just putting the flag on the context instead of the VM is much cleaner as
> far as I can see anyway.

Helper for the blind? If you gues expect me to move that myself ...
-Daniel

>
> Christian.
>
> > If there's something else that means "gpu context with it's own vm" then
> > the flag would need to be moved there, pointers appreciated (but maybe
> > someone with hw + userspace can do that quicker).
> > -Daniel
> >
> > > > Also yes this risks that a vk app which was violationing the winsys
> > > > spec will now break, which is why I think we should do this sooner
> > > > than later. Otherwise the list of w/a we might need to apply in vk
> > > > userspace will become very long :-( At least since this is purely
> > > > opt-in from userspace, we only need to have the w/a list in userspace,
> > > > where mesa has the infrastructure for that already.
> > > > -Daniel
> > > >
> > > > > Christian.
> > > > >
> > > > > > -Daniel
> > > > > >
> > > > > > > Regards,
> > > > > > > Christian.
> > > > > > >
> > > > > > > > > > The current amdgpu uapi just doesn't allow any other model without an
> > > > > > > > > > explicit opt-in. So current implicit sync userspace just has to
> > > > > > > > > > oversync, there's not much choice.
> > > > > > > > > >
> > > > > > > > > > > 2) Have an EXPLICIT fence owner that is used for explicit submissions
> > > > > > > > > > > that is ignored by AMDGPU_SYNC_NE_OWNER.
> > > > > > > > > > >
> > > > > > > > > > > But this doesn't solve cross-driver interactions here.
> > > > > > > > > > Yeah cross-driver is still entirely unsolved, because
> > > > > > > > > > amdgpu_bo_explicit_sync() on the bo didn't solve that either.
> > > > > > > > > Hui? You have lost me. Why is that still unsolved?
> > > > > > > > The part we're trying to solve with this patch is Vulkan should not
> > > > > > > > participate in any implicit sync at all wrt submissions (and then
> > > > > > > > handle the implicit sync for WSI explicitly using the fence
> > > > > > > > import/export stuff that Jason wrote). As long we add shared fences to
> > > > > > > > the dma_resv we participate in implicit sync (at the level of an
> > > > > > > > implicit sync read) still, at least from the perspective of later jobs
> > > > > > > > waiting on these fences.
> > > > > > > >
> > > > > > > > > Regards,
> > > > > > > > > Christian.
> > > > > > > > >
> > > > > > > > > > -Daniel
> > > > > > > > > >
> > > > > > > > > > > > Cc: mesa-dev@lists.freedesktop.org
> > > > > > > > > > > > Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
> > > > > > > > > > > > Cc: Dave Airlie <airlied@gmail.com>
> > > > > > > > > > > > Cc: Rob Clark <robdclark@chromium.org>
> > > > > > > > > > > > Cc: Kristian H. Kristensen <hoegsberg@google.com>
> > > > > > > > > > > > Cc: Michel Dänzer <michel@daenzer.net>
> > > > > > > > > > > > Cc: Daniel Stone <daniels@collabora.com>
> > > > > > > > > > > > Cc: Sumit Semwal <sumit.semwal@linaro.org>
> > > > > > > > > > > > Cc: "Christian König" <christian.koenig@amd.com>
> > > > > > > > > > > > Cc: Alex Deucher <alexander.deucher@amd.com>
> > > > > > > > > > > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > > > > > > > > > > Cc: Deepak R Varma <mh12gx2825@gmail.com>
> > > > > > > > > > > > Cc: Chen Li <chenli@uniontech.com>
> > > > > > > > > > > > Cc: Kevin Wang <kevin1.wang@amd.com>
> > > > > > > > > > > > Cc: Dennis Li <Dennis.Li@amd.com>
> > > > > > > > > > > > Cc: Luben Tuikov <luben.tuikov@amd.com>
> > > > > > > > > > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > > > > > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > > > > > > > > ---
> > > > > > > > > > > > drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 7 +++++--
> > > > > > > > > > > > drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 21 +++++++++++++++++++++
> > > > > > > > > > > > drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 6 ++++++
> > > > > > > > > > > > include/uapi/drm/amdgpu_drm.h | 10 ++++++++++
> > > > > > > > > > > > 4 files changed, 42 insertions(+), 2 deletions(-)
> > > > > > > > > > > >
> > > > > > > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > > > > > > > > > > > index 65df34c17264..c5386d13eb4a 100644
> > > > > > > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > > > > > > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > > > > > > > > > > > @@ -498,6 +498,7 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
> > > > > > > > > > > > struct amdgpu_bo *gds;
> > > > > > > > > > > > struct amdgpu_bo *gws;
> > > > > > > > > > > > struct amdgpu_bo *oa;
> > > > > > > > > > > > + bool no_implicit_sync = READ_ONCE(fpriv->vm.no_implicit_sync);
> > > > > > > > > > > > int r;
> > > > > > > > > > > >
> > > > > > > > > > > > INIT_LIST_HEAD(&p->validated);
> > > > > > > > > > > > @@ -577,7 +578,8 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
> > > > > > > > > > > >
> > > > > > > > > > > > e->bo_va = amdgpu_vm_bo_find(vm, bo);
> > > > > > > > > > > >
> > > > > > > > > > > > - if (bo->tbo.base.dma_buf && !amdgpu_bo_explicit_sync(bo)) {
> > > > > > > > > > > > + if (bo->tbo.base.dma_buf &&
> > > > > > > > > > > > + !(no_implicit_sync || amdgpu_bo_explicit_sync(bo))) {
> > > > > > > > > > > > e->chain = dma_fence_chain_alloc();
> > > > > > > > > > > > if (!e->chain) {
> > > > > > > > > > > > r = -ENOMEM;
> > > > > > > > > > > > @@ -649,6 +651,7 @@ static int amdgpu_cs_sync_rings(struct amdgpu_cs_parser *p)
> > > > > > > > > > > > {
> > > > > > > > > > > > struct amdgpu_fpriv *fpriv = p->filp->driver_priv;
> > > > > > > > > > > > struct amdgpu_bo_list_entry *e;
> > > > > > > > > > > > + bool no_implicit_sync = READ_ONCE(fpriv->vm.no_implicit_sync);
> > > > > > > > > > > > int r;
> > > > > > > > > > > >
> > > > > > > > > > > > list_for_each_entry(e, &p->validated, tv.head) {
> > > > > > > > > > > > @@ -656,7 +659,7 @@ static int amdgpu_cs_sync_rings(struct amdgpu_cs_parser *p)
> > > > > > > > > > > > struct dma_resv *resv = bo->tbo.base.resv;
> > > > > > > > > > > > enum amdgpu_sync_mode sync_mode;
> > > > > > > > > > > >
> > > > > > > > > > > > - sync_mode = amdgpu_bo_explicit_sync(bo) ?
> > > > > > > > > > > > + sync_mode = no_implicit_sync || amdgpu_bo_explicit_sync(bo) ?
> > > > > > > > > > > > AMDGPU_SYNC_EXPLICIT : AMDGPU_SYNC_NE_OWNER;
> > > > > > > > > > > > r = amdgpu_sync_resv(p->adev, &p->job->sync, resv, sync_mode,
> > > > > > > > > > > > &fpriv->vm);
> > > > > > > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > > > > > > > > > > > index c080ba15ae77..f982626b5328 100644
> > > > > > > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > > > > > > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > > > > > > > > > > > @@ -1724,6 +1724,26 @@ int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv)
> > > > > > > > > > > > return 0;
> > > > > > > > > > > > }
> > > > > > > > > > > >
> > > > > > > > > > > > +int amdgpu_setparam_ioctl(struct drm_device *dev, void *data,
> > > > > > > > > > > > + struct drm_file *filp)
> > > > > > > > > > > > +{
> > > > > > > > > > > > + struct drm_amdgpu_setparam *setparam = data;
> > > > > > > > > > > > + struct amdgpu_fpriv *fpriv = filp->driver_priv;
> > > > > > > > > > > > +
> > > > > > > > > > > > + switch (setparam->param) {
> > > > > > > > > > > > + case AMDGPU_SETPARAM_NO_IMPLICIT_SYNC:
> > > > > > > > > > > > + if (setparam->value)
> > > > > > > > > > > > + WRITE_ONCE(fpriv->vm.no_implicit_sync, true);
> > > > > > > > > > > > + else
> > > > > > > > > > > > + WRITE_ONCE(fpriv->vm.no_implicit_sync, false);
> > > > > > > > > > > > + break;
> > > > > > > > > > > > + default:
> > > > > > > > > > > > + return -EINVAL;
> > > > > > > > > > > > + }
> > > > > > > > > > > > +
> > > > > > > > > > > > + return 0;
> > > > > > > > > > > > +}
> > > > > > > > > > > > +
> > > > > > > > > > > > const struct drm_ioctl_desc amdgpu_ioctls_kms[] = {
> > > > > > > > > > > > DRM_IOCTL_DEF_DRV(AMDGPU_GEM_CREATE, amdgpu_gem_create_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > DRM_IOCTL_DEF_DRV(AMDGPU_CTX, amdgpu_ctx_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > @@ -1742,6 +1762,7 @@ const struct drm_ioctl_desc amdgpu_ioctls_kms[] = {
> > > > > > > > > > > > DRM_IOCTL_DEF_DRV(AMDGPU_GEM_VA, amdgpu_gem_va_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > DRM_IOCTL_DEF_DRV(AMDGPU_GEM_OP, amdgpu_gem_op_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > DRM_IOCTL_DEF_DRV(AMDGPU_GEM_USERPTR, amdgpu_gem_userptr_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > + DRM_IOCTL_DEF_DRV(AMDGPU_SETPARAM, amdgpu_setparam_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
> > > > > > > > > > > > };
> > > > > > > > > > > >
> > > > > > > > > > > > static const struct drm_driver amdgpu_kms_driver = {
> > > > > > > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> > > > > > > > > > > > index ddb85a85cbba..0e8c440c6303 100644
> > > > > > > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> > > > > > > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> > > > > > > > > > > > @@ -321,6 +321,12 @@ struct amdgpu_vm {
> > > > > > > > > > > > bool bulk_moveable;
> > > > > > > > > > > > /* Flag to indicate if VM is used for compute */
> > > > > > > > > > > > bool is_compute_context;
> > > > > > > > > > > > + /*
> > > > > > > > > > > > + * Flag to indicate whether implicit sync should always be skipped on
> > > > > > > > > > > > + * this context. We do not care about races at all, userspace is allowed
> > > > > > > > > > > > + * to shoot itself with implicit sync to its fullest liking.
> > > > > > > > > > > > + */
> > > > > > > > > > > > + bool no_implicit_sync;
> > > > > > > > > > > > };
> > > > > > > > > > > >
> > > > > > > > > > > > struct amdgpu_vm_manager {
> > > > > > > > > > > > diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
> > > > > > > > > > > > index 0cbd1540aeac..9eae245c14d6 100644
> > > > > > > > > > > > --- a/include/uapi/drm/amdgpu_drm.h
> > > > > > > > > > > > +++ b/include/uapi/drm/amdgpu_drm.h
> > > > > > > > > > > > @@ -54,6 +54,7 @@ extern "C" {
> > > > > > > > > > > > #define DRM_AMDGPU_VM 0x13
> > > > > > > > > > > > #define DRM_AMDGPU_FENCE_TO_HANDLE 0x14
> > > > > > > > > > > > #define DRM_AMDGPU_SCHED 0x15
> > > > > > > > > > > > +#define DRM_AMDGPU_SETPARAM 0x16
> > > > > > > > > > > >
> > > > > > > > > > > > #define DRM_IOCTL_AMDGPU_GEM_CREATE DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_CREATE, union drm_amdgpu_gem_create)
> > > > > > > > > > > > #define DRM_IOCTL_AMDGPU_GEM_MMAP DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_GEM_MMAP, union drm_amdgpu_gem_mmap)
> > > > > > > > > > > > @@ -71,6 +72,7 @@ extern "C" {
> > > > > > > > > > > > #define DRM_IOCTL_AMDGPU_VM DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_VM, union drm_amdgpu_vm)
> > > > > > > > > > > > #define DRM_IOCTL_AMDGPU_FENCE_TO_HANDLE DRM_IOWR(DRM_COMMAND_BASE + DRM_AMDGPU_FENCE_TO_HANDLE, union drm_amdgpu_fence_to_handle)
> > > > > > > > > > > > #define DRM_IOCTL_AMDGPU_SCHED DRM_IOW(DRM_COMMAND_BASE + DRM_AMDGPU_SCHED, union drm_amdgpu_sched)
> > > > > > > > > > > > +#define DRM_IOCTL_AMDGPU_SETPARAM DRM_IOW(DRM_COMMAND_BASE + DRM_AMDGPU_SETPARAM, struct drm_amdgpu_setparam)
> > > > > > > > > > > >
> > > > > > > > > > > > /**
> > > > > > > > > > > > * DOC: memory domains
> > > > > > > > > > > > @@ -306,6 +308,14 @@ union drm_amdgpu_sched {
> > > > > > > > > > > > struct drm_amdgpu_sched_in in;
> > > > > > > > > > > > };
> > > > > > > > > > > >
> > > > > > > > > > > > +#define AMDGPU_SETPARAM_NO_IMPLICIT_SYNC 1
> > > > > > > > > > > > +
> > > > > > > > > > > > +struct drm_amdgpu_setparam {
> > > > > > > > > > > > + /* AMDGPU_SETPARAM_* */
> > > > > > > > > > > > + __u32 param;
> > > > > > > > > > > > + __u32 value;
> > > > > > > > > > > > +};
> > > > > > > > > > > > +
> > > > > > > > > > > > /*
> > > > > > > > > > > > * This is not a reliable API and you should expect it to fail for any
> > > > > > > > > > > > * number of reasons and have fallback path that do not use userptr to
> > > > > > > > > > > > --
> > > > > > > > > > > > 2.32.0.rc2
> > > > > > > > > > > >
> > > >
> > > > --
> > > > Daniel Vetter
> > > > Software Engineer, Intel Corporation
> > > > https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C517f0d3467324e7ce05008d936581f60%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637600574408265873%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=tc6ZdgYzOXpER4vpuOiOlyIsr7YTAHLMcuFaNjSs6YE%3D&amp;reserved=0
>

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Daniel Vetter
Software Engineer, Intel Corporation