KVM: host.volume.encryption always false with qemu-img >= 10.1 (help header changed to "Supported image formats:")

从 QemuImg.helpSupportsImageFormat() 开始，然后跟踪其结果经过 LibvirtComputingResource.hostSupportsVolumeEncryption() 的路径。针对 legacy header 和 QEMU 10.1 header 验证现有的 qemu-img 格式检测，为新 header 和缺失的格式添加覆盖，并运行相关的 QemuImg 测试；完成标准是两个 header 都能检测到 LUKS，且不会匹配到不支持的格式。

problem

On KVM hosts running qemu-img 10.1.0 or newer, the agent reports
host.volume.encryption = false even though the host fully supports LUKS
volume encryption (qemu-img lists the luks format and cryptsetup is
installed). As a result, encrypted service/disk offerings cannot be deployed
on affected hosts and encrypted volumes fail placement.

Root cause — a string mismatch after a QEMU change.

LibvirtComputingResource.hostSupportsVolumeEncryption() first checks whether
qemu-img supports the LUKS format and returns early if not, so cryptsetup is
never reached. The result is stored as host.volume.encryption.

The LUKS check is in QemuImg.helpSupportsImageFormat():

Pattern pattern = Pattern.compile(
    "Supported\\sformats:[a-zA-Z0-9-_\\s]*?\\b" + format + "\\b",
    CASE_INSENSITIVE);

The anchor Supported\sformats: expects Supported + one whitespace +
formats:. QEMU changed this header in 10.1.0:

qemu-img version	--help header
<= 10.0.0	Supported formats:
>= 10.1.0	Supported image formats:

(qemu-img.c: printf("\nSupported image formats:\n");)

The inserted word image breaks the match, so supportsImageFormat(LUKS)
returns false and host.volume.encryption is stored as false. The luks
format is still in the list — it is just never matched.

Evidence — regex against the real host output:
current regex -> NO match (the bug):
$ qemu-img --help 2>&1 | grep -iP 'Supported\sformats:[a-zA-Z0-9-\s]*?\bluks\b'
(empty)
with "image" optional -> matches:
$ qemu-img --help 2>&1 | grep -izoP 'Supported\s(image\s)?formats:[a-zA-Z0-9-\s]*?\bluks\b'
Supported image formats:
... io_uring luks

Verified end-to-end: after making image optional in the regex,
host.volume.encryption flipped from false to true on affected hosts, with no
other change.

versions

• Apache CloudStack: 4.22.1.0 (affected code path is unchanged on main)
• Hypervisor: KVM on RHEL 9.8
• qemu-kvm 10.1.0 (qemu-kvm-10.1.0-17.el9_8.3), qemu-img 10.1.0
• libvirt 11.10.0
• cryptsetup: installed and functional
• Primary storage: SharedMountPoint

Actual qemu-img --help on an affected host:

qemu-img version 10.1.0 (qemu-kvm-10.1.0-17.el9_8.3)
...
Supported image formats:
  blkdebug blklogwrites blkverify compress copy-before-write copy-on-read
  file ftp ftps host_cdrom host_device http https io_uring luks nbd null-aio
  null-co nvme nvme-io_uring preallocate qcow2 quorum raw rbd
  snapshot-access throttle vdi vhdx virtio-blk-vfio-pci
  virtio-blk-vhost-user virtio-blk-vhost-vdpa vmdk vpc

The steps to reproduce the bug

1. Prepare a KVM host with qemu-img >= 10.1.0 (e.g. RHEL 9.8) and cryptsetup installed.
2. Add the host to CloudStack, or restart the agent so it re-reports host details.
3. Check the stored value:

   SELECT h.name, hd.value
   FROM host h
   JOIN host_details hd ON hd.host_id = h.id
   WHERE hd.name = 'host.volume.encryption';

Expected: host.volume.encryption = true
Actual: host.volume.encryption = false on every host with qemu-img >= 10.1.0

What to do about it?

Make the image keyword optional in the detection regex in
QemuImg.helpSupportsImageFormat() — minimal and backward compatible:

-        Pattern pattern = Pattern.compile("Supported\\sformats:[a-zA-Z0-9-_\\s]*?\\b" + format + "\\b", CASE_INSENSITIVE);
+        // QEMU >= 10.1.0 changed the qemu-img --help header from
+        // "Supported formats:" to "Supported image formats:".
+        Pattern pattern = Pattern.compile("Supported\\s(image\\s)?formats:[a-zA-Z0-9-_\\s]*?\\b" + format + "\\b", CASE_INSENSITIVE);

Supported\s(image\s)?formats: matches both the old and the new header; the
format list itself is untouched. Suggested unit tests (new header, legacy
header, negative case):

@Test
public void testHelpSupportsImageFormatQemu101Header() {
    String help =
        "Supported image formats:\n" +
        "  file ftp ftps host_cdrom host_device http https io_uring luks nbd\n";
    Assert.assertTrue(QemuImg.helpSupportsImageFormat(help, QemuImg.PhysicalDiskFormat.LUKS));
}

@Test
public void testHelpSupportsImageFormatLegacyHeader() {
    String help = "Supported formats: blkdebug file luks nbd qcow2 raw rbd vmdk\n";
    Assert.assertTrue(QemuImg.helpSupportsImageFormat(help, QemuImg.PhysicalDiskFormat.LUKS));
}

@Test
public void testHelpDoesNotSupportMissingFormat() {
    String help = "Supported image formats:\n  file qcow2 raw\n";
    Assert.assertFalse(QemuImg.helpSupportsImageFormat(help, QemuImg.PhysicalDiskFormat.LUKS));
}