Support default block interfaces per QEMUMachine

There are QEMUMachines that have neither IF_IDE nor IF_SCSI as a
default/standard interface to their block devices / drives. Therefore,
this patch introduces a new field default_block_type per QEMUMachine
struct. The prior use_scsi field becomes thereby obsolete and is
replaced through .default_block_type = IF_SCSI.

This patch also changes the default for s390x to IF_VIRTIO and
removes an early hack that converts IF_IDE drives.
Other parties have already claimed interest (e.g. IF_SD for exynos)

To create a sane default, for machines that dont specify a
default_block_type, this patch makes IF_IDE = 0 and IF_NONE = 1.
I checked all users of IF_NONE (blockdev.c and ww/device-hotplug.c)
as well as IF_IDE and it seems that it is ok to change the defines -
in other words, I found no obvious (to me) assumption in the code
regarding IF_NONE==0. IF_NONE is only set if there is an
explicit if=none. Without if=* the interface becomes IF_DEFAULT.

I would suggest to have some additional care, e.g. by letting
this patch sit some days in the block tree.

Based on an initial patch from Einar Lueck <elelueck@de.ibm.com>

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: Igor Mitsyanko <i.mitsyanko@samsung.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Igor Mitsyanko <i.mitsyanko@samsung.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/blockdev.c b/blockdev.c
index e73fd6e388..4a4d99f223 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -275,7 +275,7 @@ static bool do_check_io_limits(BlockIOLimit *io_limits)
     return true;
 }
 
-DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
+DriveInfo *drive_init(QemuOpts *opts, BlockInterfaceType block_default_type)
 {
     const char *buf;
     const char *file = NULL;
@@ -325,7 +325,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
             return NULL;
 	}
     } else {
-        type = default_to_scsi ? IF_SCSI : IF_IDE;
+        type = block_default_type;
     }
 
     max_devs = if_max_devs[type];