[Intel-gfx] [PATCH] drm/i915: Setup all page directories for gen8

[Mika Kuoppala]

If the mappable size is less than what the full range
of pdps can address, we end up setting pdps for only the
mappable area.

The logical context however needs valid pdp entries.
Prior to commit 06fda602dbca ("drm/i915: Create page table allocators")
we just have been writing pdp entries with dma address of zero instead
of valid pdps. This is supposedly bad even if those pdps are not
addressed.

As commit 06fda602dbca ("drm/i915: Create page table allocators")
introduced more dynamic structure for pdps, we ended up oopsing
when we populated the lrc context. Analyzing this oops revealed
the fact that we have not been writing valid pdps with bsw, as
it is doing the ppgtt init with 2gb limit.

We should do the right thing and setup the non addressable part
pdps/pde/pte to scratch page through the minimal structure by
having just pdp with pde entries pointing to same page with
pte entries pointing to scratch page.

But instead of going through that trouble, setup all the pdps
through individual pd pages and pt entries, even for non
addressable parts. This way we populate the lrc with valid
pdps and gives us a base for dynamic page allocation to
introduce code that truncates the page table structure.

The regression of oopsing in init was introduced by
commit 06fda602dbca ("drm/i915: Create page table allocators")

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89350
Tested-by: Valtteri Rantala <valtteri.rantala at intel.com>
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Ben Widawsky <benjamin.widawsky at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index bd95776..848a821 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -709,7 +709,7 @@ static int gen8_ppgtt_setup_page_tables(struct i915_hw_ppgtt *ppgtt,
  */
 static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt, uint64_t size)
 {
-	const int max_pdp = DIV_ROUND_UP(size, 1 << 30);
+	const int max_pdp = GEN8_LEGACY_PDPES;
 	const int min_pt_pages = GEN8_PDES_PER_PAGE * max_pdp;
 	int i, j, ret;
 
-- 
1.9.1