On Fri, Oct 21, 2016 at 01:57:28PM +0100, Chris Wilson wrote: > On Fri, Oct 21, 2016 at 02:30:32PM +0200, Daniel Vetter wrote: > > On Thu, Oct 20, 2016 at 05:00:35PM +0200, Takashi Iwai wrote: > > > On Thu, 20 Oct 2016 16:56:04 +0200, > > > Ville Syrjälä wrote: > > > > > > > > On Thu, Oct 20, 2016 at 04:39:52PM +0200, Takashi Iwai wrote: > > > > > Since 4.7 kernel, we've seen the error messages like > > > > > > > > > > kernel: [TTM] Buffer eviction failed > > > > > kernel: qxl 0000:00:02.0: object_init failed for (4026540032, 0x00000001) > > > > > kernel: [drm:qxl_alloc_bo_reserved [qxl]] *ERROR* failed to allocate VRAM BO > > > > > > > > > > on QXL when switching and accessing on VT. The culprit was the > > > > > generic deferred_io code (qxl driver switched to it since 4.7). > > > > > There is a race between the dirty clip update and the call of > > > > > callback. > > > > > > > > > > In drm_fb_helper_dirty(), the dirty clip is updated in the spinlock, > > > > > while it kicks off the update worker outside the spinlock. Meanwhile > > > > > the update worker clears the dirty clip in the spinlock, too. Thus, > > > > > when drm_fb_helper_dirty() is called concurrently, schedule_work() is > > > > > called after the clip is cleared in the first worker call. > > > > > > > > > > This patch addresses it by validating the clip before calling the > > > > > dirty fb callback. > > > > > > > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98322 > > > > > Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1003298 > > > > > Fixes: eaa434defaca ('drm/fb-helper: Add fb_deferred_io support') > > > > > Cc: <stable@xxxxxxxxxxxxxxx> > > > > > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> > > > > > --- > > > > > drivers/gpu/drm/drm_fb_helper.c | 13 +++++++++---- > > > > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > > > > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > > > > > index 03414bde1f15..d790d205129e 100644 > > > > > --- a/drivers/gpu/drm/drm_fb_helper.c > > > > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > > > > @@ -636,15 +636,20 @@ static void drm_fb_helper_dirty_work(struct work_struct *work) > > > > > dirty_work); > > > > > struct drm_clip_rect *clip = &helper->dirty_clip; > > > > > struct drm_clip_rect clip_copy; > > > > > + bool dirty; > > > > > unsigned long flags; > > > > > > > > > > spin_lock_irqsave(&helper->dirty_lock, flags); > > > > > - clip_copy = *clip; > > > > > - clip->x1 = clip->y1 = ~0; > > > > > - clip->x2 = clip->y2 = 0; > > > > > + dirty = (clip->x1 < clip->x2 && clip->y1 < clip->y2); > > > > > + if (dirty) { > > > > > + clip_copy = *clip; > > > > > + clip->x1 = clip->y1 = ~0; > > > > > + clip->x2 = clip->y2 = 0; > > > > > + } > > > > > spin_unlock_irqrestore(&helper->dirty_lock, flags); > > > > > > > > > > - helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1); > > > > > + if (dirty) > > > > > > > > Could do it the other way too, ie. just make the copy, and then check the > > > > copy (can be done after dropping the lock even). Would avoid having to > > > > add the 'dirty' variable. > > > > > > Sounds good. Let me try... > > > > Another thing: How do we prevent userspace from doing the same, i.e. > > submitting an empty rectangle? Do we need to patch up > > drm_mode_dirtyfb_ioctl too? Not much point if we fix this bug in the fb > > helpers and leave the barn door wide open for userspace to oops drivers > > ;-) > > I think of a use for sending an empty clip: where you don't want to > push any new pixel data, but you do want to be sure that the pipeline > has been flushed. What exactly should an empty rectangle flush out? It's a bit unclear, but for speed I guess drivers should be allowed to make dirty async ... -Daniel > > The change I would suggest here would be > > dirty = clip->x1 <= clip->x2 && clip->y1 <= clip->y2 > > as the bug is not the empty rectangle but the invalid one. However, that > may be overkill, and none of the backends care about the empty rect! > > But, indeed, we do not validate the incoming dirtyfb either. > > diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c > index 49fd7db758e0..ada6a5517945 100644 > --- a/drivers/gpu/drm/drm_framebuffer.c > +++ b/drivers/gpu/drm/drm_framebuffer.c > @@ -504,10 +504,13 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev, > } > > if (num_clips && clips_ptr) { > + int i; > + > if (num_clips < 0 || num_clips > DRM_MODE_FB_DIRTY_MAX_CLIPS) { > ret = -EINVAL; > goto out_err1; > } > + > clips = kcalloc(num_clips, sizeof(*clips), GFP_KERNEL); > if (!clips) { > ret = -ENOMEM; > @@ -520,6 +523,14 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev, > ret = -EFAULT; > goto out_err2; > } > + > + for (i = 0; i < num_clips; i++) { > + if (clips[i].x2 < clips[i].x1 || > + clips[i].y2 < clips[i].y1) { > + ret = -EINVAL; > + goto out_err2; > + } > + } > } > > if (fb->funcs->dirty) > > > -- > Chris Wilson, Intel Open Source Technology Centre > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
