[libvirt] [PATCH] qemu: command: Don't skip 'readonly' and throttling info for empty drive

[Peter Krempa]

In commit f80eae8c2ae I was too agresive in removing properties of
-drive for empty drives. It turns out that qemu actually persists the
state of 'readonly' and the throttling information even for the empty
drive.

Removing 'readonly' thus made qemu open any subsequent images added via
the 'change' command as RW which was forbidden by selinux thanks to the
restrictive sVirt label for readonly media.

Fix this by formating the property again and bump the tests and leave a
note detailing why the rest of the properties needs to be skipped.

Signed-off-by: Peter Krempa <pkrempa at redhat.com>
---
 src/qemu/qemu_command.c                        | 18 +++++++++++++-----
 tests/qemuxml2argvdata/disk-cdrom.args         |  4 ++--
 .../disk-cdrom.x86_64-2.12.0.args              |  4 ++--
 .../disk-cdrom.x86_64-latest.args              |  4 ++--
 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index a59583fb75..6d3aa69569 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1764,10 +1764,18 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         }
     }

+    if (disk->src->readonly)
+        virBufferAddLit(&opt, ",readonly=on");
+
+    /* qemu rejects some parameters for an empty -drive, so we need to skip
+     * them in that case:
+     * cache: modifies properties of the format driver which is not present
+     * copy_on_read: really only works for floppies
+     * discard: modifies properties of format driver
+     * detect_zeroes: works but really depends on discard so it's useless
+     * iomode: setting it to 'native' requires a specific cache mode
+     */
     if (!virStorageSourceIsEmpty(disk->src)) {
-        if (disk->src->readonly)
-            virBufferAddLit(&opt, ",readonly=on");
-
         if (disk->cachemode) {
             virBufferAsprintf(&opt, ",cache=%s",
                               qemuDiskCacheV2TypeToString(disk->cachemode));
@@ -1792,10 +1800,10 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
             virBufferAsprintf(&opt, ",aio=%s",
                               virDomainDiskIoTypeToString(disk->iomode));
         }
-
-        qemuBuildDiskThrottling(disk, &opt);
     }

+    qemuBuildDiskThrottling(disk, &opt);
+
     if (virBufferCheckError(&opt) < 0)
         goto error;

diff --git a/tests/qemuxml2argvdata/disk-cdrom.args b/tests/qemuxml2argvdata/disk-cdrom.args
index a9f60aa477..4823ae82de 100644
--- a/tests/qemuxml2argvdata/disk-cdrom.args
+++ b/tests/qemuxml2argvdata/disk-cdrom.args
@@ -27,7 +27,7 @@ bootindex=1 \
 -drive file=/root/boot.iso,format=raw,if=none,id=drive-ide0-0-1,media=cdrom,\
 readonly=on \
 -device ide-drive,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1 \
--drive if=none,id=drive-ide0-1-0,media=cdrom \
+-drive if=none,id=drive-ide0-1-0,media=cdrom,readonly=on \
 -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 \
--drive if=none,id=drive-ide0-1-1,media=cdrom \
+-drive if=none,id=drive-ide0-1-1,media=cdrom,readonly=on \
 -device ide-drive,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1
diff --git a/tests/qemuxml2argvdata/disk-cdrom.x86_64-2.12.0.args b/tests/qemuxml2argvdata/disk-cdrom.x86_64-2.12.0.args
index a39d920f67..2fe84177b8 100644
--- a/tests/qemuxml2argvdata/disk-cdrom.x86_64-2.12.0.args
+++ b/tests/qemuxml2argvdata/disk-cdrom.x86_64-2.12.0.args
@@ -28,10 +28,10 @@ file=/tmp/lib/domain--1-QEMUGuest1/master-key.aes \
 -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 \
 -drive file=/root/boot.iso,format=raw,if=none,id=drive-ide0-0-1,readonly=on \
 -device ide-cd,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1 \
--drive if=none,id=drive-ide0-1-0 \
+-drive if=none,id=drive-ide0-1-0,readonly=on \
 -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0,\
 write-cache=on \
--drive if=none,id=drive-ide0-1-1 \
+-drive if=none,id=drive-ide0-1-1,readonly=on \
 -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1 \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
 resourcecontrol=deny \
diff --git a/tests/qemuxml2argvdata/disk-cdrom.x86_64-latest.args b/tests/qemuxml2argvdata/disk-cdrom.x86_64-latest.args
index 029ae23dfa..9b9451f435 100644
--- a/tests/qemuxml2argvdata/disk-cdrom.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/disk-cdrom.x86_64-latest.args
@@ -28,10 +28,10 @@ file=/tmp/lib/domain--1-QEMUGuest1/master-key.aes \
 -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 \
 -drive file=/root/boot.iso,format=raw,if=none,id=drive-ide0-0-1,readonly=on \
 -device ide-cd,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1 \
--drive if=none,id=drive-ide0-1-0 \
+-drive if=none,id=drive-ide0-1-0,readonly=on \
 -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0,\
 write-cache=on \
--drive if=none,id=drive-ide0-1-1 \
+-drive if=none,id=drive-ide0-1-1,readonly=on \
 -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1 \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
 resourcecontrol=deny \
-- 
2.20.1