[PATCH] qemu: Don't build cache= cmd line for scsi-block

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

Trying to set any cache for <disk device='lun'/> makes no sense.
Such disk translates into -device scsi-block on the command line
and the device lacks any cache setting because it's merely a
middle man between qemu and real SCSI device.

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/qemu/qemu_command.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 7408f6bc70..c7ff074e29 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1824,6 +1824,11 @@ qemuBuildDriveDevCacheStr(virDomainDiskDefPtr disk,
     if (disk->cachemode == VIR_DOMAIN_DISK_CACHE_DEFAULT)
         return 0;
 
+    /* VIR_DOMAIN_DISK_DEVICE_LUN translates into 'scsi-block'
+     * where any caching setting makes no sense. */
+    if (disk->device == VIR_DOMAIN_DISK_DEVICE_LUN)
+        return 0;
+
     if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DISK_WRITE_CACHE))
         return 0;
 
-- 
2.16.1

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