[Intel-gfx] [PATCH xf86-video-intel] SNA: fix PRIME output support since xserver 1.20

[Peter Wu]

Ping.

This patch was independently verified working (see the linked bug
report) and is essential for Xorg 1.20 using this driver.

On Tue, Aug 14, 2018 at 02:16:07AM +0200, Peter Wu wrote:
> Since xorg-server 1.20, an external monitor would remain blank when used
> in a PRIME output slave setup. Only a cursor was visible. The cause is
> "Make PixmapDirtyUpdateRec::src a DrawablePtr" in xserver, the "src"
> pointer might point to the root window (created by the server) instead
> of a pixmap (as created by xf86-video-intel). Use get_drawable_pixmap to
> handle both cases.
> 
> When built with -fsanitize=address, the following test will trigger a
> heap-buffer-overflow error due to to_sna_from_pixmap receiving a window
> instead of a pixmap.
> 
> Test on a hybrid graphics laptop (Intel + modesetting/nouveau):
> 
>     xrandr --setprovideroutputsource modesetting Intel
>     xrandr --output DP-1-1 --mode 2560x1440  # should not crash
>     glxgears  # should display gears on both screens
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100086
> Signed-off-by: Peter Wu <peter at lekensteyn.nl>
> ---
> Tested with xserver 1.20.1 with ASAN enabled. Survives multiple
> resolution changes, works with a Plasma desktop session, it seems
> stable. Something like this patch is required to make multi-monitor
> setups usable in a hybrid graphics setting with Xorg 1.20.
> ---
>  src/sna/sna_accel.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/src/sna/sna_accel.c b/src/sna/sna_accel.c
> index 2f669bcf..80b116a3 100644
> --- a/src/sna/sna_accel.c
> +++ b/src/sna/sna_accel.c
> @@ -17510,7 +17510,11 @@ static bool has_offload_slaves(struct sna *sna)
>  	PixmapDirtyUpdatePtr dirty;
>  
>  	xorg_list_for_each_entry(dirty, &screen->pixmap_dirty_list, ent) {
> +#ifdef HAS_DIRTYTRACKING_DRAWABLE_SRC
> +		assert(dirty->src == &sna->front->drawable);
> +#else
>  		assert(dirty->src == sna->front);
> +#endif
>  		if (RegionNotEmpty(DamageRegion(dirty->damage)))
>  			return true;
>  	}
> @@ -17671,7 +17675,11 @@ static void sna_accel_post_damage(struct sna *sna)
>  		if (RegionNil(damage))
>  			continue;
>  
> +#ifdef HAS_DIRTYTRACKING_DRAWABLE_SRC
> +		src = get_drawable_pixmap(dirty->src);
> +#else
>  		src = dirty->src;
> +#endif
>  		dst = dirty->slave_dst->master_pixmap;
>  
>  		region.extents.x1 = dirty->x;
> @@ -17922,9 +17930,15 @@ migrate_dirty_tracking(PixmapPtr old_front, PixmapPtr new_front)
>  	PixmapDirtyUpdatePtr dirty, safe;
>  
>  	xorg_list_for_each_entry_safe(dirty, safe, &screen->pixmap_dirty_list, ent) {
> +#ifdef HAS_DIRTYTRACKING_DRAWABLE_SRC
> +		assert(dirty->src == &old_front->drawable);
> +		if (dirty->src != &old_front->drawable)
> +			continue;
> +#else
>  		assert(dirty->src == old_front);
>  		if (dirty->src != old_front)
>  			continue;
> +#endif
>  
>  		DamageUnregister(&dirty->src->drawable, dirty->damage);
>  		DamageDestroy(dirty->damage);
> @@ -17939,7 +17953,11 @@ migrate_dirty_tracking(PixmapPtr old_front, PixmapPtr new_front)
>  		}
>  
>  		DamageRegister(&new_front->drawable, dirty->damage);
> +#ifdef HAS_DIRTYTRACKING_DRAWABLE_SRC
> +		dirty->src = &new_front->drawable;
> +#else
>  		dirty->src = new_front;
> +#endif
>  	}
>  #endif
>  }
> -- 
> 2.18.0