Revert "block/vpc: Fix size calculation"

This reverts commit f880defb.

Jeff Cody's testing revealed that the interpretation of size differs
even between VirtualPC and HyperV.  Revert this so there is time to
consider the impact of any backwards incompatible behavior this change
creates.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/vpc.c

@@ -34,8 +34,6 @@
 
 #define HEADER_SIZE 512
 
-#define VHD_SECTOR_SIZE 512
-
 //#define CACHE
 
 enum vhd_type {
@@ -206,13 +204,11 @@ static int vpc_open(BlockDriverState *bs, int flags)
     /* Write 'checksum' back to footer, or else will leave it with zero. */
     footer->checksum = be32_to_cpu(checksum);
 
-    /* The visible size of a image in Virtual PC depends on the guest:
-     * QEMU and other emulators report the real size (here in sectors).
-     * All modern operating systems use this real size.
-     * Very old operating systems use CHS values to calculate the total size.
-     * This calculated size is usually smaller than the real size.
-     */
-    bs->total_sectors = be64_to_cpu(footer->size) / VHD_SECTOR_SIZE;
+    // The visible size of a image in Virtual PC depends on the geometry
+    // rather than on the size stored in the footer (the size in the footer
+    // is too large usually)
+    bs->total_sectors = (int64_t)
+        be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl;
 
     /* Allow a maximum disk size of approximately 2 TB */
     if (bs->total_sectors >= 65535LL * 255 * 255) {