FreeBSD: don't set the MTRR if it's the default mode (uncacheable).

1 files changed, 5 insertions, 2 deletions

diff --git a/src/freebsd_pci.c b/src/freebsd_pci.c
index 84a0a78..be934a8 100644
--- a/src/freebsd_pci.c
+++ b/src/freebsd_pci.c
@@ -108,8 +108,11 @@ pci_device_freebsd_map_range(struct pci_device *dev,
     mro.mo_desc = &mrd;
     mro.mo_arg[0] = MEMRANGE_SET_UPDATE;
 
-    if (ioctl(fd, MEMRANGE_SET, &mro)) {
-	fprintf(stderr, "failed to set mtrr: %s\n", strerror(errno));
+    /* No need to set an MTRR if it's the default mode. */
+    if (mrd.mr_flags != MDF_UNCACHEABLE) {
+	if (ioctl(fd, MEMRANGE_SET, &mro)) {
+	    fprintf(stderr, "failed to set mtrr: %s\n", strerror(errno));
+	}
     }
 
     close(fd);