drm/i915/error: skip non-mappable pages

Skip capturing any lmem pages that can't be copied using the CPU. This
in now only best effort on platforms that have small BAR.

Testcase: igt@gem-exec-capture@capture-invisible
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629174350.384910-7-matthew.auld@intel.com

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -1129,11 +1129,15 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 		dma_addr_t dma;
 
 		for_each_sgt_daddr(dma, iter, vma_res->bi.pages) {
+			dma_addr_t offset = dma - mem->region.start;
 			void __iomem *s;
 
-			s = io_mapping_map_wc(&mem->iomap,
-					      dma - mem->region.start,
-					      PAGE_SIZE);
+			if (offset + PAGE_SIZE > mem->io_size) {
+				ret = -EINVAL;
+				break;
+			}
+
+			s = io_mapping_map_wc(&mem->iomap, offset, PAGE_SIZE);
 			ret = compress_page(compress,
 					    (void __force *)s, dst,
 					    true);