Re: [Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk
On Fri, Nov 04, 2016 at 09:36:31AM +, Chris Wilson wrote:
> On Fri, Nov 04, 2016 at 10:50:44AM +0200, Joonas Lahtinen wrote:
> > On ke, 2016-11-02 at 09:43 +, Chris Wilson wrote:
> > > @@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct
> > > drm_i915_gem_object *obj)
> > > if (err)
> > > return err;
> > >
> > > - if (likely(obj->mm.pages)) {
> > > - __i915_gem_object_pin_pages(obj);
> > > - goto unlock;
> > > - }
> > > -
> > > - GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> > > + if (unlikely(!obj->mm.pages)) {
> > > + GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> > > + err = i915_gem_object_get_pages(obj);
> > > + if (err)
> > > + goto unlock;
> > >
> > > - err = i915_gem_object_get_pages(obj);
> > > - if (!err)
> > > - atomic_set_release(>mm.pages_pin_count, 1);
> > > + smp_mb__before_atomic();
> >
> > This is not cool without atomic in sight. Inline wrap as
> > __i915_gem_object_pages_mb() or something.
>
> My first thought was to put in i915_gem_object_get_pages() since it
> closes the action of setting up the obj->mm.pages and co. I didn't like
> that because the association then with the use of the pages_pin_count as
> the mutex was not as apparent. Now that you cannot see the atomic_inc()
> at all here, you are left confused!
>
> Would you rather this just used the raw atomic_inc() here?
Actually, I like using atomics better here. It is definitely consistent
as we then don't mix the raw atomics and the helpers.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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Re: [Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk
On Fri, Nov 04, 2016 at 10:50:44AM +0200, Joonas Lahtinen wrote:
> On ke, 2016-11-02 at 09:43 +, Chris Wilson wrote:
> > @@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct
> > drm_i915_gem_object *obj)
> > if (err)
> > return err;
> >
> > - if (likely(obj->mm.pages)) {
> > - __i915_gem_object_pin_pages(obj);
> > - goto unlock;
> > - }
> > -
> > - GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> > + if (unlikely(!obj->mm.pages)) {
> > + GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> > + err = i915_gem_object_get_pages(obj);
> > + if (err)
> > + goto unlock;
> >
> > - err = i915_gem_object_get_pages(obj);
> > - if (!err)
> > - atomic_set_release(>mm.pages_pin_count, 1);
> > + smp_mb__before_atomic();
>
> This is not cool without atomic in sight. Inline wrap as
> __i915_gem_object_pages_mb() or something.
My first thought was to put in i915_gem_object_get_pages() since it
closes the action of setting up the obj->mm.pages and co. I didn't like
that because the association then with the use of the pages_pin_count as
the mutex was not as apparent. Now that you cannot see the atomic_inc()
at all here, you are left confused!
Would you rather this just used the raw atomic_inc() here?
>
> > @@ -3707,6 +3707,7 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
> > {
> > int ret = 0;
> >
> > + GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
>
> Rather confusing, simple mind would think as
> __i915_gem_object_pin_pages has GEM_BUG_ON(!obj->mm.pages),
> the next branch would never be taken?
GEM_BUG_ON(vma == obj) ? Sorry not parsing very well this morning.
GEM_BUG_ON(!obj->mm.pages) would be a weaker form of the above. The
challenge is to express that the vma->page is only valid for the current
lifespan of the obj->mm.pages, should we regenerate that sg_table, we
need to regenerate the vma->pages. So I want to say that we must be
holding a pages_pin_count to utilize the vma->pages.
> > if (vma->pages)
> > return 0;
--
Chris Wilson, Intel Open Source Technology Centre
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Re: [Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk
On ke, 2016-11-02 at 09:43 +, Chris Wilson wrote:
> @@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct
> drm_i915_gem_object *obj)
> if (err)
> return err;
>
> - if (likely(obj->mm.pages)) {
> - __i915_gem_object_pin_pages(obj);
> - goto unlock;
> - }
> -
> - GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> + if (unlikely(!obj->mm.pages)) {
> + GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> + err = i915_gem_object_get_pages(obj);
> + if (err)
> + goto unlock;
>
> - err = i915_gem_object_get_pages(obj);
> - if (!err)
> - atomic_set_release(>mm.pages_pin_count, 1);
> + smp_mb__before_atomic();
This is not cool without atomic in sight. Inline wrap as
__i915_gem_object_pages_mb() or something.
> @@ -3707,6 +3707,7 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
> {
> int ret = 0;
>
> + GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
Rather confusing, simple mind would think as
__i915_gem_object_pin_pages has GEM_BUG_ON(!obj->mm.pages),
the next branch would never be taken?
> if (vma->pages)
> return 0;
>
Regards, Joonas
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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Re: [Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk
On Wed, Nov 02, 2016 at 09:43:54AM +, Chris Wilson wrote:
> commit bc0629a76726 ("drm/i915: Track pages pinned due to swizzling
> quirk") fixed one problem, but revealed a whole lot more. The root cause
> of the pin count mismatch for the swizzle quirk (for L-shaped memory on
> gen3/4) was that we were incrementing the pages_pin_count upon getting
> the backing pages but then overwriting the pages_pin_count to set it to
> 1 afterwards. With a little bit of adjustment to satisfy the GEM_BUG_ON
> sanitychecks, the fix is to replace the explicit atomic_set with an
> atomic_inc.
>
> Fixes: 1233e2db199d ("drm/i915: Move object backing storage manipulation")
> Signed-off-by: Chris Wilson
> Cc: Joonas Lahtinen
> Cc: Tvrtko Ursulin
Ping?
> ---
> drivers/gpu/drm/i915/i915_gem.c| 40
> ++
> drivers/gpu/drm/i915/i915_gem_gtt.c| 1 +
> drivers/gpu/drm/i915/i915_gem_tiling.c | 1 +
> 3 files changed, 23 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 993fb90da104..5fe7562aefbd 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2386,12 +2386,6 @@ i915_gem_object_get_pages_gtt(struct
> drm_i915_gem_object *obj)
> if (i915_gem_object_needs_bit17_swizzle(obj))
> i915_gem_object_do_bit_17_swizzle(obj, st);
>
> - if (i915_gem_object_is_tiled(obj) &&
> - dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
> - __i915_gem_object_pin_pages(obj);
> - obj->mm.quirked = true;
> - }
> -
> return st;
>
> err_pages:
> @@ -2424,6 +2418,13 @@ void __i915_gem_object_set_pages(struct
> drm_i915_gem_object *obj,
> obj->mm.get_page.sg_idx = 0;
>
> obj->mm.pages = pages;
> +
> + if (i915_gem_object_is_tiled(obj) &&
> + to_i915(obj->base.dev)->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
> + GEM_BUG_ON(obj->mm.quirked);
> + __i915_gem_object_pin_pages(obj);
> + obj->mm.quirked = true;
> + }
> }
>
> static int i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
> @@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct
> drm_i915_gem_object *obj)
> if (err)
> return err;
>
> - if (likely(obj->mm.pages)) {
> - __i915_gem_object_pin_pages(obj);
> - goto unlock;
> - }
> -
> - GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> + if (unlikely(!obj->mm.pages)) {
> + GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> + err = i915_gem_object_get_pages(obj);
> + if (err)
> + goto unlock;
>
> - err = i915_gem_object_get_pages(obj);
> - if (!err)
> - atomic_set_release(>mm.pages_pin_count, 1);
> + smp_mb__before_atomic();
> + }
>
> + __i915_gem_object_pin_pages(obj);
> unlock:
> mutex_unlock(>mm.lock);
> return err;
> @@ -2542,8 +2542,8 @@ void *i915_gem_object_pin_map(struct
> drm_i915_gem_object *obj,
> if (ret)
> goto err_unlock;
>
> - GEM_BUG_ON(atomic_read(>mm.pages_pin_count));
> - atomic_set_release(>mm.pages_pin_count, 1);
> + smp_mb__before_atomic();
> + __i915_gem_object_pin_pages(obj);
> pinned = false;
> }
> GEM_BUG_ON(!obj->mm.pages);
> @@ -2578,7 +2578,7 @@ void *i915_gem_object_pin_map(struct
> drm_i915_gem_object *obj,
> return ptr;
>
> err_unpin:
> - atomic_dec(>mm.pages_pin_count);
> + __i915_gem_object_unpin_pages(obj);
> err_unlock:
> ptr = ERR_PTR(ret);
> goto out_unlock;
> @@ -2996,7 +2996,7 @@ int i915_vma_unbind(struct i915_vma *vma)
> goto destroy;
>
> GEM_BUG_ON(obj->bind_count == 0);
> - GEM_BUG_ON(!obj->mm.pages);
> + GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
>
> if (i915_vma_is_map_and_fenceable(vma)) {
> /* release the fence reg _after_ flushing */
> @@ -3230,6 +3230,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64
> alignment, u64 flags)
> list_move_tail(>global_list, _priv->mm.bound_list);
> list_move_tail(>vm_link, >vm->inactive_list);
> obj->bind_count++;
> + GEM_BUG_ON(atomic_read(>mm.pages_pin_count) < obj->bind_count);
>
> return 0;
>
> @@ -4282,6 +4283,7 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void
> *data,
> obj->mm.quirked = false;
> }
> if (args->madv == I915_MADV_WILLNEED) {
> + GEM_BUG_ON(obj->mm.quirked);
> __i915_gem_object_pin_pages(obj);
> obj->mm.quirked = true;
> }
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
>
