nouveau: fix storing invalid ptes

When migrating a range of system memory to device private memory, some of
the pages in the address range may not be migrating. In this case, the non
migrating pages won't have a new GPU MMU entry to store but the
nvif_object_ioctl() NVIF_VMM_V0_PFNMAP method doesn't check the input and
stores a bad valid GPU page table entry.

Fix this by skipping the invalid input PTEs when updating the GPU page
tables.

Link: https://lore.kernel.org/r/20200723223004.9586-2-rcampbell@nvidia.comSigned-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c

@@ -79,8 +79,12 @@ gp100_vmm_pgt_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt *pt,
 	dma_addr_t addr;
 
 	nvkm_kmap(pt->memory);
-	while (ptes--) {
+	for (; ptes; ptes--, map->pfn++) {
 		u64 data = 0;
+
+		if (!(*map->pfn & NVKM_VMM_PFN_V))
+			continue;
+
 		if (!(*map->pfn & NVKM_VMM_PFN_W))
 			data |= BIT_ULL(6); /* RO. */
 
@@ -100,7 +104,6 @@ gp100_vmm_pgt_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt *pt,
 		}
 
 		VMM_WO064(pt, vmm, ptei++ * 8, data);
-		map->pfn++;
 	}
 	nvkm_done(pt->memory);
 }
@@ -310,9 +313,12 @@ gp100_vmm_pd0_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt *pt,
 	dma_addr_t addr;
 
 	nvkm_kmap(pt->memory);
-	while (ptes--) {
+	for (; ptes; ptes--, map->pfn++) {
 		u64 data = 0;
 
+		if (!(*map->pfn & NVKM_VMM_PFN_V))
+			continue;
+
 		if (!(*map->pfn & NVKM_VMM_PFN_W))
 			data |= BIT_ULL(6); /* RO. */
 
@@ -332,7 +338,6 @@ gp100_vmm_pd0_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt *pt,
 		}
 
 		VMM_WO064(pt, vmm, ptei++ * 16, data);
-		map->pfn++;
 	}
 	nvkm_done(pt->memory);
 }