[PATCH] i915: Add support for drm syncobjs
Chris Wilson
chris at chris-wilson.co.uk
Wed Jul 5 18:42:06 UTC 2017
Quoting Jason Ekstrand (2017-07-05 19:32:21)
> On Wed, Jul 5, 2017 at 10:37 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Quoting Jason Ekstrand (2017-07-05 18:21:22)
> > This commit adds support for waiting on or signaling DRM syncobjs as
> > part of execbuf. It does so by hijacking the currently unused cliprects
> > pointer to instead point to an array of i915_gem_exec_fence structs
> > which containe a DRM syncobj and a flags parameter which specifies
> > whether to wait on it or to signal it. This implementation
> > theoretically allows for both flags to be set in which case it waits on
> > the dma_fence that was in the syncobj and then immediately replaces it
> > with the dma_fence from the current execbuf.
> >
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >
> > Ideally, I'd like to get whatever kernel reviewing and/or merging is
> > required to land the userspace bits ASAP. That said, I understand that
> > this is my first kernel patch and it's liable to have a few rounds of
> > review before going in. :-)
> >
> > The mesa branch for using this in Vulkan can be found here:
> >
> > https://cgit.freedesktop.org/~jekstrand/mesa/log/?h=review/anv-syncobj
> >
> > drivers/gpu/drm/i915/i915_drv.c | 3 +-
> > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 97
> ++++++++++++++++++++++++++++--
> > include/uapi/drm/i915_drm.h | 30 ++++++++-
> > 3 files changed, 121 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_
> drv.c
> > index 9167a73..e6f7f49 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -384,6 +384,7 @@ static int i915_getparam(struct drm_device *dev, void
> *data,
> > case I915_PARAM_HAS_EXEC_FENCE:
> > case I915_PARAM_HAS_EXEC_CAPTURE:
> > case I915_PARAM_HAS_EXEC_BATCH_FIRST:
> > + case I915_PARAM_HAS_EXEC_FENCE_ARRAY:
> > /* For the time being all of these are always true;
> > * if some supported hardware does not have one of these
> > * features this value needs to be provided from
> > @@ -2734,7 +2735,7 @@ static struct drm_driver driver = {
> > */
> > .driver_features =
> > DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED | DRIVER_GEM |
> DRIVER_PRIME |
> > - DRIVER_RENDER | DRIVER_MODESET | DRIVER_ATOMIC,
> > + DRIVER_RENDER | DRIVER_MODESET | DRIVER_ATOMIC |
> DRIVER_SYNCOBJ,
> > .release = i915_driver_release,
> > .open = i915_driver_open,
> > .lastclose = i915_driver_lastclose,
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm
> /i915/i915_gem_execbuffer.c
> > index 929f275..81b7b7b 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -33,6 +33,7 @@
> >
> > #include <drm/drmP.h>
> > #include <drm/i915_drm.h>
> > +#include <drm/drm_syncobj.h>
> >
> > #include "i915_drv.h"
> > #include "i915_gem_clflush.h"
> > @@ -1882,8 +1883,10 @@ static bool i915_gem_check_execbuffer(struct
> drm_i915_gem_execbuffer2 *exec)
> > return false;
> >
> > /* Kernel clipping was a DRI1 misfeature */
> > - if (exec->num_cliprects || exec->cliprects_ptr)
> > - return false;
> > + if (!(exec->flags & I915_EXEC_FENCE_ARRAY)) {
> > + if (exec->num_cliprects || exec->cliprects_ptr)
> > + return false;
> > + }
> >
> > if (exec->DR4 == 0xffffffff) {
> > DRM_DEBUG("UXA submitting garbage DR4, fixing up\n");
> > @@ -2118,12 +2121,15 @@ static int
> > i915_gem_do_execbuffer(struct drm_device *dev,
> > struct drm_file *file,
> > struct drm_i915_gem_execbuffer2 *args,
> > - struct drm_i915_gem_exec_object2 *exec)
> > + struct drm_i915_gem_exec_object2 *exec,
> > + struct drm_i915_gem_exec_fence *fences)
> > {
> > struct i915_execbuffer eb;
> > struct dma_fence *in_fence = NULL;
> > struct sync_file *out_fence = NULL;
> > + struct drm_syncobj **syncobjs = NULL;
> > int out_fence_fd = -1;
> > + unsigned int i;
> > int err;
> >
> > BUILD_BUG_ON(__EXEC_OBJECT_INTERNAL_FLAGS &
> > @@ -2186,9 +2192,30 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> > }
> > }
> >
> > + if (args->flags & I915_EXEC_FENCE_ARRAY) {
> > + syncobjs = kvmalloc_array(args->num_cliprects,
> > + sizeof(*syncobjs),
> > + __GFP_NOWARN | GFP_TEMPORARY |
> > + __GFP_ZERO);
> > + if (syncobjs == NULL) {
> > + DRM_DEBUG("Failed to allocate array of %d
> syncobjs\n",
> > + args->num_cliprects);
> > + err = -ENOMEM;
> > + goto err_out_fence;
> > + }
> > + for (i = 0; i < args->num_cliprects; i++) {
> > + syncobjs[i] = drm_syncobj_find(file, fences
> [i].handle);
> > + if (!syncobjs[i]) {
> > + DRM_DEBUG("Invalid syncobj handle
> provided\n");
> > + err = -EINVAL;
> > + goto err_syncobjs;
> > + }
> > + }
>
> I did this in the caller so that we only allocated and passed in a single
> array of drm_syncobj (with the flags packed into the low bits).
>
>
> Packing things into the low bits seems a bit sketchy but it works so long as we
> only have the two flag bits.
>
>
> > + }
> > +
> > err = eb_create(&eb);
> > if (err)
> > - goto err_out_fence;
> > + goto err_syncobjs;
> >
> > GEM_BUG_ON(!eb.lut_size);
> >
> > @@ -2304,6 +2331,16 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> > goto err_request;
> > }
> >
> > + if (args->flags & I915_EXEC_FENCE_ARRAY) {
> > + for (i = 0; i < args->num_cliprects; i++) {
> > + if (fences[i].flags & I915_EXEC_FENCE_WAIT) {
> > + if (i915_gem_request_await_dma_fence
> (eb.request,
> > +
> syncobjs[i]->fence))
> > + goto err_request;
> > + }
> > + }
> > + }
> > +
> > if (out_fence_fd != -1) {
> > out_fence = sync_file_create(&eb.request->fence);
> > if (!out_fence) {
> > @@ -2312,6 +2349,20 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> > }
> > }
> >
> > + /* We need to add fences to syncobjs last because doing so mutates
> the
> > + * syncobj and we have no good way to recover if the execbuf fails
> > + * after this point. Fortunately, drm_syncobj_replace_fence can
> never
> > + * fail.
> > + */
> > + if (args->flags & I915_EXEC_FENCE_ARRAY) {
> > + for (i = 0; i < args->num_cliprects; i++) {
> > + if (fences[i].flags & I915_EXEC_FENCE_SIGNAL) {
> > + drm_syncobj_replace_fence(file, syncobjs
> [i],
> > + &eb.request->
> fence);
> > + }
> > + }
> > + }
> > +
>
> This has to be after the execbuf is submitted, next to where out_fence
> is attached is a good spot, and should only be updated on success. (The
> kernel API allows combining of FENCE_WAIT | FENCE_SIGNAL so we can only
> replace a FENCE_WAIT once we know we have committed the execbuf.)
>
>
> It's currently right after we call
>
> out_fence = sync_file_create(&eb.request->fence);
That's where we create the out fence, not where we attach it to the
request, see the fd_install, which is after we have successfully
committed the request.
> which is before eb_submit(). Are sync files wrong? Note that I was careful to
> ensure that there are no error paths after syncobj_replace_fence so we know for
> 100% sure that it will be committed, hence the comment.
There's the rather big one in eb_submit() that will generate EINTR for
your pain.
> I moved all of these to little functions: get_fence_array,
> await_fence_array, signal_fence_array and put_fence_array.
>
>
> You clearly have a version of this patch somewhere. Where can I find it?
It's still on the older syncobj api, I am easily distracted. :|
-Chris
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