[Mesa-dev] [Request for Testing] i965: import prime buffers in the current context, not screen

[Kristian Høgsberg]

On Thu, Aug 25, 2016 at 11:38 AM, Chad Versace <chadversary at chromium.org> wrote:
> On Thu 25 Aug 2016, Martin Peres wrote:
>> This mirrors the codepath taken by DRI2 in IntelSetTexBuffer2() and
>> fixes many applications when using DRI3:
>>  - Totem with libva on hw-accelerated decoding
>>  - obs-studio, using Window Capture (Xcomposite) as a Source
>>  - gstreamer with VAAPI
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71759
>> Signed-off-by: Martin Peres <martin.peres at linux.intel.com>
>> ---
>>
>> This patch supposedly prevents gnome from running for one Arch Linux
>> maintainer. Kenneth Graunke  and I failed to reproduce it so I am
>> asking for your help/comments on this.
>>
>>  src/mesa/drivers/dri/i965/intel_screen.c | 24 ++++++++++++++++++++++--
>>  1 file changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
>> index 7876652..5c0d300 100644
>> --- a/src/mesa/drivers/dri/i965/intel_screen.c
>> +++ b/src/mesa/drivers/dri/i965/intel_screen.c
>> @@ -698,8 +698,11 @@ intel_create_image_from_fds(__DRIscreen *screen,
>>                              int *fds, int num_fds, int *strides, int *offsets,
>>                              void *loaderPrivate)
>>  {
>> +   GET_CURRENT_CONTEXT(ctx);
>>     struct intel_screen *intelScreen = screen->driverPrivate;
>> +   struct brw_context *brw = brw_context(ctx);
>>     struct intel_image_format *f;
>> +   dri_bufmgr *bufmgr;
>>     __DRIimage *image;
>>     int i, index;
>>
>> @@ -740,8 +743,25 @@ intel_create_image_from_fds(__DRIscreen *screen,
>>           size = end;
>>     }
>>
>> -   image->bo = drm_intel_bo_gem_create_from_prime(intelScreen->bufmgr,
>> -                                                  fds[0], size);
>> +   /* Let's import the buffer into the current context instead of the current
>> +    * screen as some applications like gstreamer, totem, or obs create multiple
>> +    * X connections which end up creating multiple screens and thus multiple
>> +    * buffer managers. They then proceed to use a different X connection to call
>> +    * GLXBindTexImageExt() which should import the buffer in the current thread
>> +    * bound and not the current screen. This is done properly upstairs for
>> +    * texture management so we need to mirror this behaviour if we don't want
>> +    * the kernel rejecting our pushbuffers as the buffers have not been imported
>> +    * by the same bufmgr that sent the pushbuffer.
>> +    *
>> +    * If there is no context currently bound, then revert to using the screen's
>> +    * buffer manager and hope for the best...
>
> Nope. This patch breaks EGL_EXT_image_dma_buf_import.
>
> When the user calls eglCreateImageKHR(EGLDisplay, EGLContext, ...) with
> image type EGL_LINUX_DMA_BUF_EXT, then the spec requires that context be
> NULL. The EGLDisplay parameter determines the namespace of the newly created
> EGLImage. By design, the currently bound context (and its display) DO NOT affect
> eglCreateImage.
>
>   Problem Example:
>     eglMakeCurrent(dpyA, ..., ctxA);
>     img = eglCreateImage(dpyB, EGL_NO_CONTEXT, ...);

The difference between DRI2 and DRI3 is that for DRI2 we'd get a
DRI2Buffer back from getBuffers, and then open the flink name inside
the driver with the current context's bufmgr. In the DRI3 world, we go
from prime fd to drm_bo in dri3_get_pixmap_buffer() with the screen
that's associated with the current drawable.

I think the fix we're looking for is to make
draw->vtable->get_dri_context() also return the __DRIscreen, then use
that in dri3_get_pixmap_buffer() to get the right __DRIscreen to pass
to loader_dri3_create_image().

Kristian

>> +    */
>> +   if (brw)
>> +       bufmgr = brw->bufmgr;
>> +   else
>> +       bufmgr = intelScreen->bufmgr;
>> +
>> +   image->bo = drm_intel_bo_gem_create_from_prime(bufmgr, fds[0], size);
>>     if (image->bo == NULL) {
>>        free(image);
>>        return NULL;
>> --
>> 2.9.3
>>
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