qemu: domain: Reject copy_on_read for read-only disks

The sectors read from the backing image need to be written to the top
level image. If a disk is marked read-only the image can't be written.

QEMU handled that by disabling copy_on_read and reporting a warning:

-drive file=/var/lib/libvirt/images/c,format=qcow2,if=none,
    id=drive-scsi0-0-1,readonly=on,copy-on-read=on:
    warning: disabling copy-on-read on read-only drive

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Peter Krempa 2018-07-10 10:18:53 +02:00
parent 9ac3ea5cf8
commit d7eeafaa4c

View File

@ -4650,6 +4650,13 @@ qemuDomainDeviceDefValidateDisk(const virDomainDiskDef *disk,
return -1;
}
if (disk->src->readonly && disk->copy_on_read == VIR_TRISTATE_SWITCH_ON) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
_("copy_on_read is not compatible with read-only disk '%s'"),
disk->dst);
return -1;
}
if (disk->geometry.cylinders > 0 &&
disk->geometry.heads > 0 &&
disk->geometry.sectors > 0) {