[PATCH xserver] modesetting: Fix msSharePixmapBacking returning a non-linear bo

[Keith Packard]

Hans de Goede <hdegoede at redhat.com> writes:

> Some code paths end up in msSharePixmapBacking with a pixmap
> which does not have its usage_hint set to sharable.
>
> This causes glamor_fd_from_pixmap() to create a non-linear bo,
> which is wrong for a shared pixmap.
>
> This commits sets the pixmap usage hint to shared before
> calling glamor_fd_from_pixmap(), fixing this.
>
> Specifically this fixes mis-rendering when running the mode
> setting driver on the master gpu in a dual-gpu setup and
> running an opengl app with DRI_PRIME=1.
>
> One could argue that this is a problem of the caller, but the
> usage_hint is as the name implies just a hint. I've tried
> tracing the DRI_PRIME case from above, but the pixmap
> ends up coming from a drawable passed into the server by
> a client.
>
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  hw/xfree86/drivers/modesetting/driver.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/hw/xfree86/drivers/modesetting/driver.c b/hw/xfree86/drivers/modesetting/driver.c
> index 5ebb394..023d491 100644
> --- a/hw/xfree86/drivers/modesetting/driver.c
> +++ b/hw/xfree86/drivers/modesetting/driver.c
> @@ -1382,7 +1382,12 @@ msSharePixmapBacking(PixmapPtr ppix, ScreenPtr screen, void **handle)
>      int ret;
>      CARD16 stride;
>      CARD32 size;
> +    unsigned orig_usage_hint = ppix->usage_hint;
> +
> +    /* Ensure that glamor_fd_from_pixmap creates a sharable (linear) bo */
> +    ppix->usage_hint = CREATE_PIXMAP_USAGE_SHARED;
>      ret = glamor_fd_from_pixmap(ppix->drawable.pScreen, ppix, &stride, &size);
> +    ppix->usage_hint = orig_usage_hint;

That just can't be the right way to fix this... Not that I have a better
idea at this point.

-- 
-keith
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