tools/guest-diag: fbcopy_pub maps BAR1 at any offset (nonzero-offset mmaps work on this mdev; offset-0 64 MB window fallback kept, pread beyond window) - SESSION 149

1 files changed, 28 insertions, 13 deletions

diff --git a/tools/guest-diag/fbcopy_pub.c b/tools/guest-diag/fbcopy_pub.c
index ecb38da..a064882 100644
--- a/tools/guest-diag/fbcopy_pub.c
+++ b/tools/guest-diag/fbcopy_pub.c
@@ -573,25 +573,40 @@ int main(int argc, char **argv)
 		int w = argc > 5 ? atoi(argv[5]) : DEF_W;
 		int h = argc > 6 ? atoi(argv[6]) : DEF_H;
 		int pitch = argc > 7 ? atoi(argv[7]) : DEF_PITCH;
-		unsigned long long need = off +
-			(unsigned long long)(h - 1) * pitch +
+		unsigned long long span = (unsigned long long)(h - 1) * pitch +
 			(unsigned long long)w * 4;
-		size_t wlen = 0;
+		unsigned long long base = off & ~0xfffULL;
+		size_t wlen = (size_t)((off - base) + span);
 		unsigned char *wmap;
 		int f, y, x;
 
-		wmap = map_vram(vram_fd, map_size, &wlen);
-		if (!wmap) {
-			printf("WIN_MAP_FAIL len=0x%zx\n", wlen);
+		if (off + span > map_size) {
+			printf("OFF_RANGE_FAIL need=0x%llx bar=0x%zx\n",
+			       off + span, map_size);
 			return 1;
 		}
-		if (need > wlen) {
-			printf("OFF_RANGE_FAIL need=0x%llx window=0x%zx\n",
-			       need, wlen);
-			return 1;
+		/* 2026-10-28 (session 149): nonzero-offset mmaps of BAR1 work
+		 * on this mdev (earlier builds assumed only offset 0 <= 64 MB
+		 * was mappable). Map directly at the requested offset; fall
+		 * back to the old offset-0 64 MB window if that ever fails. */
+		wlen = (wlen + 0xfff) & ~0xfffUL;
+		wmap = mmap(NULL, wlen, PROT_READ, MAP_SHARED, vram_fd,
+			    (off_t)base);
+		if (wmap == MAP_FAILED) {
+			size_t got = 0;
+			wmap = map_vram(vram_fd, map_size, &got);
+			if (wmap) {
+				base = 0;
+				wlen = got;
+			}
+			if (!wmap || off + span > wlen) {
+				printf("WIN_MAP_FAIL off=0x%llx len=0x%zx errno=%d\n",
+				       base, wlen, errno);
+				return 1;
+			}
 		}
-		printf("PUB off=0x%llx frames=%d fps=%d %dx%d pitch=%d\n",
-		       off, frames, fps, w, h, pitch);
+		printf("PUB off=0x%llx base=0x%llx len=0x%zx frames=%d fps=%d %dx%d pitch=%d\n",
+		       off, base, wlen, frames, fps, w, h, pitch);
 		hdr->magic = HDR_MAGIC;
 		hdr->version = 1;
 		hdr->width = (uint32_t)w;
@@ -602,7 +617,7 @@ int main(int argc, char **argv)
 			uint64_t t0 = now_ns();
 			unsigned char *dst = bar + FRAME_OFFSET +
 					     sizeof(struct frame_hdr);
-			unsigned char *src = wmap + (size_t)off;
+			unsigned char *src = wmap + (size_t)(off - base);
 
 			for (y = 0; y < h; y++) {
 				unsigned char *s = src + (size_t)y * pitch;