[PATCH 5.19 020/155] drm/i915/ttm: fix CCS handling

Greg Kroah-Hartman
2022-09-06T14:00:40Z

From: Matthew Auld <matthew.auld@intel.com>

[ Upstream commit 8d905254162965c8e6be697d82c7dbf5d08f574d ]

Crucible + recent Mesa seems to sometimes hit:

GEM_BUG_ON(num_ccs_blks > NUM_CCS_BLKS_PER_XFER)

And it looks like we can also trigger this with gem_lmem_swapping, if we
modify the test to use slightly larger object sizes.

Looking closer it looks like we have the following issues in
migrate_copy():

- We are using plain integer in various places, which we can easily
overflow with a large object.

- We pass the entire object size (when the src is lmem) into
emit_pte() and then try to copy it, which doesn't work, since we
only have a few fixed sized windows in which to map the pages and
perform the copy. With an object > 8M we therefore aren't properly
copying the pages. And then with an object > 64M we trigger the
GEM_BUG_ON(num_ccs_blks > NUM_CCS_BLKS_PER_XFER).

So it looks like our copy handling for any object > 8M (which is our
CHUNK_SZ) is currently broken on DG2.

Fixes: da0595ae91da ("drm/i915/migrate: Evict and restore the flatccs capable lmem obj")
Testcase: igt@gem_lmem_swapping
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C<ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220805132240.442747-2-matthew.auld@intel.com
(cherry picked from commit 8676145eb2f53a9940ff70910caf0125bd8a4bc2)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/i915/gt/intel_migrate.c | 44 ++++++++++++-------------
1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c
index 2b10b96b17b5b..933648cc90ff9 100644
--- a/drivers/gpu/drm/i915/gt/intel_migrate.c
+++ b/drivers/gpu/drm/i915/gt/intel_migrate.c
@@ -638,9 +638,9 @@ static int emit_copy(struct i915_request *rq,
return 0;
}

-static int scatter_list_length(struct scatterlist *sg)
+static u64 scatter_list_length(struct scatterlist *sg)
{
- int len = 0;
+ u64 len = 0;

while (sg && sg_dma_len(sg)) {
len += sg_dma_len(sg);
@@ -650,28 +650,26 @@ static int scatter_list_length(struct scatterlist *sg)
return len;
}

-static void
+static int
calculate_chunk_sz(struct drm_i915_private *i915, bool src_is_lmem,
- int *src_sz, u32 bytes_to_cpy, u32 ccs_bytes_to_cpy)
+ u64 bytes_to_cpy, u64 ccs_bytes_to_cpy)
{
- if (ccs_bytes_to_cpy) {
- if (!src_is_lmem)
- /*
- * When CHUNK_SZ is passed all the pages upto CHUNK_SZ
- * will be taken for the blt. in Flat-ccs supported
- * platform Smem obj will have more pages than required
- * for main meory hence limit it to the required size
- * for main memory
- */
- *src_sz = min_t(int, bytes_to_cpy, CHUNK_SZ);
- } else { /* ccs handling is not required */
- *src_sz = CHUNK_SZ;
- }
+ if (ccs_bytes_to_cpy && !src_is_lmem)
+ /*
+ * When CHUNK_SZ is passed all the pages upto CHUNK_SZ
+ * will be taken for the blt. in Flat-ccs supported
+ * platform Smem obj will have more pages than required
+ * for main meory hence limit it to the required size
+ * for main memory
+ */
+ return min_t(u64, bytes_to_cpy, CHUNK_SZ);
+ else
+ return CHUNK_SZ;
}

-static void get_ccs_sg_sgt(struct sgt_dma *it, u32 bytes_to_cpy)
+static void get_ccs_sg_sgt(struct sgt_dma *it, u64 bytes_to_cpy)
{
- u32 len;
+ u64 len;

do {
GEM_BUG_ON(!it->sg || !sg_dma_len(it->sg));
@@ -702,12 +700,12 @@ intel_context_migrate_copy(struct intel_context *ce,
{
struct sgt_dma it_src = sg_sgt(src), it_dst = sg_sgt(dst), it_ccs;
struct drm_i915_private *i915 = ce->engine->i915;
- u32 ccs_bytes_to_cpy = 0, bytes_to_cpy;
+ u64 ccs_bytes_to_cpy = 0, bytes_to_cpy;
enum i915_cache_level ccs_cache_level;
u32 src_offset, dst_offset;
u8 src_access, dst_access;
struct i915_request *rq;
- int src_sz, dst_sz;
+ u64 src_sz, dst_sz;
bool ccs_is_src, overwrite_ccs;
int err;

@@ -790,8 +788,8 @@ intel_context_migrate_copy(struct intel_context *ce,
if (err)
goto out_rq;

- calculate_chunk_sz(i915, src_is_lmem, &src_sz,
- bytes_to_cpy, ccs_bytes_to_cpy);
+ src_sz = calculate_chunk_sz(i915, src_is_lmem,
+ bytes_to_cpy, ccs_bytes_to_cpy);

len = emit_pte(rq, &it_src, src_cache_level, src_is_lmem,
src_offset, src_sz);
--
2.35.1