[Intel-gfx] [PATCH 2/2] drm/i915: fully apply WaSkipStolenMemoryFirstPage
Ville Syrjälä
ville.syrjala at linux.intel.com
Thu Dec 15 13:26:59 UTC 2016
On Thu, Dec 15, 2016 at 11:23:55AM -0200, Paulo Zanoni wrote:
> Don't even tell the mm allocator to handle the first page of stolen on
> the affected platforms. This means that we won't inherit the FB in
> case the BIOS decides to put it at the start of stolen. But the BIOS
> should not be putting it at the start of stolen since it's going to
> get corrupted. I suppose the bug here is that some pixels at the very
> top of the screen will be corrupted, so it's not exactly easy to
> notice.
>
> We have confirmation that the first page of stolen does actually get
> corrupted, so I really think we should do this in order to avoid any
> possible future headaches, even if that means losing BIOS framebuffer
> inheritance. Let's not use the HW in a way it's not supposed to be
> used.
>
> Notice that now ggtt->stolen_usable_size won't reflect the ending
> address of the stolen usable range anymore, so we have to fix the
> places that rely on this. To simplify, we'll just use U64_MAX.
>
> v2: don't even put the first page on the mm (Chris)
> v3: drm_mm_init() takes size instead of end as argument (Ville)
> v4: add a comment explaining the reserved ranges (Chris)
> use 0 for start and U64_MAX for end when possible (Chris)
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
> drivers/gpu/drm/i915/i915_gem_gtt.h | 10 +++++++++-
> drivers/gpu/drm/i915/i915_gem_stolen.c | 36 ++++++++++++----------------------
> drivers/gpu/drm/i915/intel_fbc.c | 2 +-
> 3 files changed, 22 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
> index 8965bbb..0055b85 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.h
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
> @@ -315,8 +315,16 @@ struct i915_ggtt {
> struct i915_address_space base;
> struct io_mapping mappable; /* Mapping to our CPU mappable region */
>
> + /* Stolen memory is segmented in hardware with different portions
> + * offlimits to certain functions.
> + *
> + * The drm_mm is initialised to the total accessible range, as found
> + * from the PCI config. On Broadwell+, this is further restricted to
> + * avoid the first page! The upper end of stolen memory is reserved for
> + * hardware functions and similarly removed from the accessible range.
> + */
> size_t stolen_size; /* Total size of stolen memory */
> - size_t stolen_usable_size; /* Total size minus BIOS reserved */
> + size_t stolen_usable_size; /* Total size minus reserved ranges */
> size_t stolen_reserved_base;
> size_t stolen_reserved_size;
> u64 mappable_end; /* End offset that we can CPU map */
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index b1c8897..cbbfc64 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -54,12 +54,6 @@ int i915_gem_stolen_insert_node_in_range(struct drm_i915_private *dev_priv,
> if (!drm_mm_initialized(&dev_priv->mm.stolen))
> return -ENODEV;
>
> - /* See the comment at the drm_mm_init() call for more about this check.
> - * WaSkipStolenMemoryFirstPage:bdw+ (incomplete)
> - */
> - if (start < 4096 && INTEL_GEN(dev_priv) >= 8)
> - start = 4096;
> -
> mutex_lock(&dev_priv->mm.stolen_lock);
> ret = drm_mm_insert_node_in_range(&dev_priv->mm.stolen, node, size,
> alignment, start, end,
> @@ -73,11 +67,8 @@ int i915_gem_stolen_insert_node(struct drm_i915_private *dev_priv,
> struct drm_mm_node *node, u64 size,
> unsigned alignment)
> {
> - struct i915_ggtt *ggtt = &dev_priv->ggtt;
> -
> return i915_gem_stolen_insert_node_in_range(dev_priv, node, size,
> - alignment, 0,
> - ggtt->stolen_usable_size);
> + alignment, 0, U64_MAX);
Just i915_gem_stolen_insert_node() then?
> }
>
> void i915_gem_stolen_remove_node(struct drm_i915_private *dev_priv,
> @@ -410,7 +401,7 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
> {
> struct i915_ggtt *ggtt = &dev_priv->ggtt;
> unsigned long reserved_total, reserved_base = 0, reserved_size;
> - unsigned long stolen_top;
> + unsigned long stolen_usable_start, stolen_top;
>
> mutex_init(&dev_priv->mm.stolen_lock);
>
> @@ -489,20 +480,17 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
> ggtt->stolen_size >> 10,
> (ggtt->stolen_size - reserved_total) >> 10);
>
> - ggtt->stolen_usable_size = ggtt->stolen_size - reserved_total;
> + stolen_usable_start = 0;
> + /* WaSkipStolenMemoryFirstPage:bdw+ */
> + if (INTEL_GEN(dev_priv) >= 8)
> + stolen_usable_start = 4096;
>
> - /*
> - * Basic memrange allocator for stolen space.
> - *
> - * TODO: Notice that some platforms require us to not use the first page
> - * of the stolen memory but their BIOSes may still put the framebuffer
> - * on the first page. So we don't reserve this page for now because of
> - * that. Our current solution is to just prevent new nodes from being
> - * inserted on the first page - see the check we have at
> - * i915_gem_stolen_insert_node_in_range(). We may want to fix the fbcon
> - * problem later.
> - */
> - drm_mm_init(&dev_priv->mm.stolen, 0, ggtt->stolen_usable_size);
> + ggtt->stolen_usable_size = ggtt->stolen_size - reserved_total -
> + stolen_usable_start;
> +
> + /* Basic memrange allocator for stolen space. */
> + drm_mm_init(&dev_priv->mm.stolen, stolen_usable_start,
> + ggtt->stolen_usable_size);
>
> return 0;
> }
> diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
> index 62f215b..bb5f58c 100644
> --- a/drivers/gpu/drm/i915/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/intel_fbc.c
> @@ -538,7 +538,7 @@ static int find_compression_threshold(struct drm_i915_private *dev_priv,
> IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))
> end = ggtt->stolen_size - 8 * 1024 * 1024;
> else
> - end = ggtt->stolen_usable_size;
> + end = U64_MAX;
>
> /* HACK: This code depends on what we will do in *_enable_fbc. If that
> * code changes, this code needs to change as well.
> --
> 2.7.4
>
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--
Ville Syrjälä
Intel OTC
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