bz#505090: Guess host device type from requested guest device type

RHEL bug:
  https://bugzilla.redhat.com/show_bug.cgi?id=505090

Clone of the following Fedora bug:
  https://bugzilla.redhat.com/show_bug.cgi?id=473154

[ehabkost: comments from Cole Robinson on bugzilla are pasted below]

> I just went digging through the qemu code, and I think the fix should really be
> at that level.
>
> The code is already capable of being launched with an empty cdrom device
> attached to it. Unfortunately qemu only enables this mode for cdrom devices if
> the passed path starts with '/dev/cd': in the above case, we are using /dev/sr0
> :( Yay robustness.
>
> Patch basically says "If the user requests a cdrom/floppy device, and the
> passed path is a block or char device, assume the path is a host cdrom/floppy
> device." This would change some existing behavior: for example, a host block
> device that is passed to a qemu guest as a cdrom is now assumed to be a host
> cdrom, even when it isn't. My guess is this won't yield any real functional
> change, since the only differences between floppy/cdrom and everything else (in
> this case) is in the ejectable media commands.
>
> I haven't done much testing besides verifying that qemu no longer complains
> about accessing the empty /dev/sr0.

[ehabkost: patch was sent to qemu-devel at:
   http://marc.info/?l=qemu-devel&m=124458617900905
 However, the code on the upstream qemu tree is different now, and the patch
 will need to be ported when submitted again.]

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Bugzilla: 505090
RH-Upstream-status: equivalent-patch-submitted(qemu-devel)
Message-Id: <1245185205-9600-1-git-send-email-ehabkost@redhat.com>
Acked-by: Dor Laor <dlaor@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
Acked-by: john cooper <john.cooper@redhat.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/qemu/block-raw-posix.c b/qemu/block-raw-posix.c
index 85c57b8d..ac2dab9e 100644
--- a/qemu/block-raw-posix.c
+++ b/qemu/block-raw-posix.c
@@ -944,16 +944,21 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
 
     s->type = FTYPE_FILE;
 #if defined(__linux__)
-    if (strstart(filename, "/dev/cd", NULL)) {
+    if (strstart(filename, "/dev/cd", NULL) ||
+        bs->type == BDRV_TYPE_CDROM) {
         /* open will not fail even if no CD is inserted */
         open_flags |= O_NONBLOCK;
         s->type = FTYPE_CD;
-    } else if (strstart(filename, "/dev/fd", NULL)) {
+    }
+    if (strstart(filename, "/dev/fd", NULL) ||
+        bs->type == BDRV_TYPE_FLOPPY) {
         s->type = FTYPE_FD;
         s->fd_open_flags = open_flags;
         /* open will not fail even if no floppy is inserted */
         open_flags |= O_NONBLOCK;
-    } else if (strstart(filename, "/dev/sg", NULL)) {
+    }
+    if (s->type = FTYPE_FILE &&
+        strstart(filename, "/dev/sg", NULL)) {
         bs->sg = 1;
     }
 #endif