drm/i915/gtt: Fix pte clear range

Comparing pte index to a number of entries is wrong
when clearing a range of pte entries. Use end marker
of 'one past' to correctly point adequate number of
ptes to the scratch page.

v2: assert early instead of warning late (Chris)
v3: removed consts (Joonas)

Fixes: d209b9c3cd28 ("drm/i915/gtt: Split gen8_ppgtt_clear_pte_range")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98282
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reported-by: Mike Lothian <mike@fireburn.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Mike Lothian <mike@fireburn.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 00606a27e9aa289258bef625a1ec94fdb0cee031..dc279ca61974ae9c3ca9a5847dbad1e3474cbe2b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -716,9 +716,9 @@ static bool gen8_ppgtt_clear_pt(struct i915_address_space *vm,
                                uint64_t length)
 {
        struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
-       unsigned int pte_start = gen8_pte_index(start);
        unsigned int num_entries = gen8_pte_count(start, length);
-       uint64_t pte;
+       unsigned int pte = gen8_pte_index(start);
+       unsigned int pte_end = pte + num_entries;
        gen8_pte_t *pt_vaddr;
        gen8_pte_t scratch_pte = gen8_pte_encode(vm->scratch_page.daddr,
                                                 I915_CACHE_LLC);
@@ -726,7 +726,9 @@ static bool gen8_ppgtt_clear_pt(struct i915_address_space *vm,
        if (WARN_ON(!px_page(pt)))
                return false;
 
-       bitmap_clear(pt->used_ptes, pte_start, num_entries);
+       GEM_BUG_ON(pte_end > GEN8_PTES);
+
+       bitmap_clear(pt->used_ptes, pte, num_entries);
 
        if (bitmap_empty(pt->used_ptes, GEN8_PTES)) {
                free_pt(vm->dev, pt);
@@ -735,8 +737,8 @@ static bool gen8_ppgtt_clear_pt(struct i915_address_space *vm,
 
        pt_vaddr = kmap_px(pt);
 
-       for (pte = pte_start; pte < num_entries; pte++)
-               pt_vaddr[pte] = scratch_pte;
+       while (pte < pte_end)
+               pt_vaddr[pte++] = scratch_pte;
 
        kunmap_px(ppgtt, pt_vaddr);