drm/i915/ttm: fix CCS handling

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: da0595ae ("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

drivers/gpu/drm/i915/gt/intel_migrate.c

@@ -609,9 +609,9 @@ 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);
@@ -621,28 +621,26 @@ 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));
@@ -673,12 +671,12 @@ 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;
 
@@ -761,8 +759,8 @@ 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);