Re: [PATCH] i915: Add support for drm syncobjs

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Jul 5, 2017 at 10:37 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>
> ---
>
> 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);

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.
 
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?
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux