Currently libvirt doesn't confirm whether the guest has responded to the
disk removal request. In some cases this can leave the guest with
continued access to the device while the mgmt layer believes that it has
been removed. With a recent qemu monitor command[1] we can
deterministically revoke a guests access to the disk (on the QEMU side)
to ensure no futher access is permitted.
This patch adds support for the drive_del() command and introduces it
in the disk removal paths. If the guest is running in a QEMU without this
command we currently explicitly check for unknown command/CommandNotFound
and log the issue.
If QEMU supports the command we issue the drive_del command after we attempt
to remove the device. The guest may respond and remove the block device
before we get to attempt to call drive_del. In that case, we explicitly check
for 'Device not found' from the monitor indicating that the target drive
was auto-deleted upon guest responds to the device removal notification.
1. http://thread.gmane.org/gmane.comp.emulators.qemu/84745
Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Currently libvirt doesn't confirm whether the guest has responded to the
disk removal request. In some cases this can leave the guest with
continued access to the device while the mgmt layer believes that it has
been removed. With a recent qemu monitor command[1] we can
deterministically revoke a guests access to the disk (on the QEMU side)
to ensure no futher access is permitted.
This patch adds support for the drive_unplug() command and introduces it
in the disk removal paths. There is some discussion to be had about how
to handle the case where the guest is running in a QEMU without this
command (and the fact that we currently don't have a way of detecting
what monitor commands are available).
Changes since v2:
- use VIR_ERROR to report when unplug command not found
Changes since v1:
- return > 0 when command isn't present, < 0 on command failure
- detect when drive_unplug command isn't present and log error
instead of failing entire command
Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Virsh shouldn't check for driver support but rather let the backend handled this.
After removing the check, I can successfully attach file-based images to a qemu
VM with attach-disk.
% virsh attach-disk vm2 /images/test02.img vdc --driver qemu --type disk --subdriver raw
Disk attached successfully
This command generates the following XML:
<disk type='block' device='disk'>
<driver name='qemu' type='raw'/>
<source dev='/images/test02.img'/>
<target dev='vdc' bus='virtio'/>
<alias name='virtio-disk2'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
</disk>
Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Currently when we attempt to change the cdrom in a qemu VM the monitor
doesn't generate an error if the target filename doesn't exist. I've
submitted a patch[1] for this. This patch is the libvirt qemu-driver
side which catches the error message from the monitor and reportes the
error to libvirt. This means that virsh attach-disk cdrom commands
won't appear to succeed when qemu change command actually failed.
* src/qemu/qemu_monitor_text.c: in qemuMonitorTextChangeMedia() look
for failure to access the new data
Ryan Harper