drm/nouveau/vm: fix mapping of SG pages list

SG pages lists (not to be confused with scatterlists) are a list of 4KB
memory pages used to define a nouveau_mem. Mapping them to a VM that
does not use 4KB apertures resulted in each subsequent 4KB physical page
being mapped into a larger VM aperture, thus creating an incorrect,
overlapping mapping.

This patch fixes this issue by detecting when such mappings occur and by
skipping the required number of pages in the list to ensure a correct
linear mapping.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/nvkm/subdev/vm/base.c b/nvkm/subdev/vm/base.c
index f75a683bd..583463cfe 100644
--- a/nvkm/subdev/vm/base.c
+++ b/nvkm/subdev/vm/base.c
@@ -152,13 +152,18 @@ nouveau_vm_map_sg(struct nouveau_vma *vma, u64 delta, u64 length,
 		end = (pte + num);
 		if (unlikely(end >= max))
 			end = max;
-		len = end - pte;
+
+		/*
+		 * Map pages >4KB one by one so we can fix the list pointer
+		 * as to not map intermediate pages to the next PTE
+		 */
+		len = bits ? 1 : end - pte;
 
 		vmm->map_sg(vma, pgt, mem, pte, len, list);
 
 		num  -= len;
 		pte  += len;
-		list += len;
+		list += len << bits;
 		if (unlikely(end >= max)) {
 			pde++;
 			pte = 0;