[PATCH 3/3] device-assignment: Byte-wise ROM read

[Alex Williamson <alex.williamson@redhat.com>]

The host kernel filters the PCI option ROM, returning only bytes for
the actual ROM size, not for the whole BAR.  That means we typically
do a short read of the PCI sysfs ROM file.  Read it a byte at a time
so we know how much to actually copy and only skip the copy if we
get nothing.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 hw/device-assignment.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/hw/device-assignment.c b/hw/device-assignment.c
index 0e82a16..3bb7f0b 100644
--- a/hw/device-assignment.c
+++ b/hw/device-assignment.c
@@ -1680,19 +1680,20 @@ static void assigned_dev_load_option_rom(AssignedDevice *dev)
         return;
     }
 
-    ret = fread(buf, size, 1, fp);
-    if (!feof(fp) || ferror(fp) || ret != 1) {
+    if (!(ret = fread(buf, 1, size, fp))) {
         free(buf);
         fclose(fp);
         return;
     }
     fclose(fp);
 
+    /* The number of bytes read is often much smaller than the BAR size */
+    size = ret;
+
     /* Copy ROM contents into the space backing the ROM BAR */
     if (dev->v_addrs[PCI_ROM_SLOT].r_size >= size &&
         dev->v_addrs[PCI_ROM_SLOT].u.r_virtbase) {
-        memcpy(dev->v_addrs[PCI_ROM_SLOT].u.r_virtbase,
-               buf, size);
+        memcpy(dev->v_addrs[PCI_ROM_SLOT].u.r_virtbase, buf, size);
     }
 
     free(buf);