drm/nouveau/bios: require checksum to match for fast acpi shadow method

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/nouveau/nvkm/subdev/bios/priv.h

@@ -12,6 +12,7 @@ struct nvbios_source {
 	bool rw;
 	bool ignore_checksum;
 	bool no_pcir;
+	bool require_checksum;
 };
 
 int nvbios_extend(struct nvkm_bios *, u32 length);

drivers/gpu/drm/nouveau/nvkm/subdev/bios/shadow.c

@@ -86,9 +86,12 @@ shadow_image(struct nvkm_bios *bios, int idx, u32 offset, struct shadow *mthd)
 		    nvbios_checksum(&bios->data[image.base], image.size)) {
 			nvkm_debug(subdev, "%08x: checksum failed\n",
 				   image.base);
-			if (mthd->func->rw)
+			if (!mthd->func->require_checksum) {
+				if (mthd->func->rw)
+					score += 1;
 				score += 1;
-			score += 1;
+			} else
+				return 0;
 		} else {
 			score += 3;
 		}

drivers/gpu/drm/nouveau/nvkm/subdev/bios/shadowacpi.c

@@ -99,6 +99,7 @@ nvbios_acpi_fast = {
 	.init = acpi_init,
 	.read = acpi_read_fast,
 	.rw = false,
+	.require_checksum = true,
 };
 
 const struct nvbios_source