Add ./configure --with-drive-if=(ide|scsi|virtio)

With this flag the packager can decide to default to a particular
qemu drive model.  The current default is 'ide', however note that
we intend to change this in future to 'virtio' once some upstream
regressions are fixed.  Packagers can force a particular drive
model if they wish.

3 files changed, 16 insertions, 4 deletions

diff --git a/configure.ac b/configure.ac
index 03f93886..ae0d81e0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -102,6 +102,18 @@ the --with-qemu option.
     AC_MSG_RESULT([yes])
 fi
 
+dnl Set drive interface used by the guestfs_add_drive{,_ro} calls
+dnl ('-drive ...,if=...' option to qemu).
+dnl
+dnl NB. We will change the default in future to virtio, but at the
+dnl moment this causes a performance problem, RHBZ#509383.
+AC_ARG_WITH([drive-if],
+	[AS_HELP_STRING([--with-drive-if],
+	  [set default driver (ide|scsi|virtio) @<:@default=ide@:>@])],
+	[],
+	[with_drive_if=ide])
+AC_DEFINE_UNQUOTED([DRIVE_IF],["$with_drive_if"],[Default drive interface.])
+
 dnl Check for febootstrap etc.
 AC_CHECK_PROG([FEBOOTSTRAP],
 	[febootstrap],[febootstrap],[no])
diff --git a/src/generator.ml b/src/generator.ml
index f41413e8..239f021f 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -378,7 +378,7 @@ just want to read the image or write access if you want to modify the
 image).
 
 This is equivalent to the qemu parameter
-C<-drive file=filename,cache=off,if=virtio>.
+C<-drive file=filename,cache=off,if=...>.
 
 Note that this call checks for the existence of C<filename>.  This
 stops you from specifying other types of drive which are supported
@@ -412,7 +412,7 @@ handle is closed.  We don't currently have any method to enable
 changes to be committed, although qemu can support this.
 
 This is equivalent to the qemu parameter
-C<-drive file=filename,snapshot=on,if=virtio>.
+C<-drive file=filename,snapshot=on,if=...>.
 
 Note that this call checks for the existence of C<filename>.  This
 stops you from specifying other types of drive which are supported
diff --git a/src/guestfs.c b/src/guestfs.c
index 9cdb2dde..c3bce0b8 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -708,7 +708,7 @@ guestfs_add_drive (guestfs_h *g, const char *filename)
   }
 
   /* cache=off improves reliability in the event of a host crash. */
-  snprintf (buf, len, "file=%s,cache=off,if=virtio", filename);
+  snprintf (buf, len, "file=%s,cache=off,if=%s", filename, DRIVE_IF);
 
   return guestfs_config (g, "-drive", buf);
 }
@@ -729,7 +729,7 @@ guestfs_add_drive_ro (guestfs_h *g, const char *filename)
     return -1;
   }
 
-  snprintf (buf, len, "file=%s,snapshot=on,if=virtio", filename);
+  snprintf (buf, len, "file=%s,snapshot=on,if=%s", filename, DRIVE_IF);
 
   return guestfs_config (g, "-drive", buf);
 }