vhd creation ============ There is currently a hard dependency on the patched version of ``vhd-utils`` to create Xenserver VHD compatible images. The main target for these images is the Rackspace Public Cloud. This note should explain the current issues. The patch to include ``convert`` as an option to ``vhd-utils``, avaialble at https://github.com/citrix-openstack/xenserver-utils/, is built by infra into a PPA available at https://launchpad.net/~openstack-ci-core/+archive/ubuntu/vhd-util. Upstream Xen has actually removed all the code related to ``blktap2`` with https://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=5c883cf036cf5ab8b1b79390549e2475f7a568dd. The tools have been removed from Debuntu with https://bugs.debian.org/917907. So this patch is even less trivial to apply; the project has seemingly been split into https://github.com/xapi-project/blktap/ but support status is unclear. It is tempting to use ``qemu-img`` image conversion routines. Indeed this supports converting RAW images to VPC output. However, VPC is a fairly flexible standard across a number of different hypervisors. The main standard is available from Microsoft at https://www.microsoft.com/en-us/download/confirmation.aspx?id=23850 and is what ``qemu-img`` impelements. However, trying to boot an image created with this results in a "resize" error. This is described in https://bugs.launchpad.net/nova/+bug/862653 but comes down to the following in https://github.com/xapi-project/blktap/blob/master/vhd/lib/vhd-util-resize.c#L1055:: if (!vhd_creator_tapdisk(&vhd)) { printf("%s not created by xen; resize not supported\n", name); err = -EINVAL; } It seems that Xen will refuse to grow a image without a creator ``tap\0``. It is tempting to patch ``qemu-img`` to do this (patch follows for those interested). However, if you look at the output with ``vhd-util read -p -n ./.vhd`` you will notice it complains about an invalid ``batmap``. The ``batmap`` appears to be a Xen extension to the VPC standard. Checking ``vhd_has_batmap`` at https://github.com/xen-project/xen/blob/365aabb6e5023cee476adf81106729efd49c644f/tools/blktap2/vhd/lib/libvhd.c#L1193 it seems we can fool Xen by setting the vhd version tags low enough that it thinks the image doesn't have a ``batmap`` (i.e. presumably created with tools before ``batmap``'s existed). Side note: there is a bunch of qemu work to implement overlay VHD disks with https://patchwork.ozlabs.org/project/qemu-devel/list/?submitter=64750 which has never merged. This also seems to include a ``batmap`` implementation. With the full patch applied below, we get images that appear fairly similar from (patched) ``vhd-util`` and ``qemu-img``; generated from the same ``.raw`` file. qemu-img output:: VHD Footer Summary: ------------------- Cookie : conectix Features : (0x00000002) File format version : Major: 1, Minor: 0 Data offset : 512 Timestamp : Wed Oct 30 06:25:41 2019 Creator Application : 'tap' Creator version : Major: 1, Minor: 0 Creator OS : Unknown! Original disk size : 16667 MB (17477591040 Bytes) Current disk size : 16667 MB (17477591040 Bytes) Geometry : Cyl: 33865, Hds: 16, Sctrs: 63 : = 16667 MB (17477591040 Bytes) Disk type : Dynamic hard disk Checksum : 0xffffec8c|0xffffec8c (Good!) UUID : 1bfda481-dd4d-43aa-8f3a-84689b5ab3d7 Saved state : No Hidden : 0 VHD Header Summary: ------------------- Cookie : cxsparse Data offset (unusd) : 18446744073709 Table offset : 1536 Header version : 0x00010000 Max BAT size : 8334 Block size : 2097152 (2 MB) Parent name : Parent UUID : 00000000-0000-0000-0000-000000000000 Parent timestamp : Sat Jan 1 00:00:00 2000 Checksum : 0xfffff3c9|0xfffff3c9 (Good!) vhd-utils output:: VHD Footer Summary: ------------------- Cookie : conectix Features : (0x00000002) File format version : Major: 1, Minor: 0 Data offset : 512 Timestamp : Tue Oct 8 09:18:54 2019 Creator Application : 'tap' Creator version : Major: 1, Minor: 3 Creator OS : Unknown! Original disk size : 16668 MB (17477664768 Bytes) Current disk size : 16668 MB (17477664768 Bytes) Geometry : Cyl: 33865, Hds: 16, Sctrs: 63 : = 16667 MB (17477591040 Bytes) Disk type : Dynamic hard disk Checksum : 0xffffeebb|0xffffeebb (Good!) UUID : 14f2710a-b9b8-48f7-94bb-005ba6d566b2 Saved state : No Hidden : 0 VHD Header Summary: ------------------- Cookie : cxsparse Data offset (unusd) : 18446744073709 Table offset : 1536 Header version : 0x00010000 Max BAT size : 8334 Block size : 2097152 (2 MB) Parent name : Parent UUID : 00000000-0000-0000-0000-000000000000 Parent timestamp : Sat Jan 1 00:00:00 2000 Checksum : 0xfffff3c9|0xfffff3c9 (Good!) VHD Batmap Summary: ------------------- Batmap offset : 35840 Batmap size (secs) : 3 Batmap version : 0x00010002 Checksum : 0xfffbf214|0xfffbf214 (Good!) This does upload and boot in RAX, but the root disk does not appear to grow correctly. Emperically, it also seems that fixed sized disks (generated with ``subformat=fixed``) will not import (at least into Rackspace). I also tried resizing the dynamic ``vhd`` (with ``vhd-util resize --debug -n ./test.vhd -s $((32 * 1024 * 1024 )) -j resize.log``), which looked correct in ``vhd-util`` output (``Current disk size`` grew) but Rackspace would not import this image. qemu patch ========== Applies against qemu at HEAD ``16884391c750d0c5e863f55ad7aaaa146fc5181e`` :: diff --git a/block/vpc.c b/block/vpc.c index a655502..d1716f0 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -60,6 +60,7 @@ enum vhd_type { #define VHD_MAX_GEOMETRY (VHD_CHS_MAX_C * VHD_CHS_MAX_H * VHD_CHS_MAX_S) #define VPC_OPT_FORCE_SIZE "force_size" +#define VPC_OPT_XENSERVER_COMPAT "xenserver_compat" /* always big-endian */ typedef struct vhd_footer { @@ -1042,12 +1043,16 @@ static int coroutine_fn vpc_co_create(BlockdevCreateOptions *opts, memset(buf, 0, 1024); memcpy(footer->creator, "conectix", 8); - if (vpc_opts->force_size) { + if (vpc_opts->xenserver_compat) { + memcpy(footer->creator_app, "tap\0", 4); + memcpy(footer->creator_os, "\0\0\0\0", 4); + } else if (vpc_opts->force_size) { memcpy(footer->creator_app, "qem2", 4); + memcpy(footer->creator_os, "Wi2k", 4); } else { memcpy(footer->creator_app, "qemu", 4); + memcpy(footer->creator_os, "Wi2k", 4); } - memcpy(footer->creator_os, "Wi2k", 4); footer->features = cpu_to_be32(0x02); footer->version = cpu_to_be32(0x00010000); @@ -1058,9 +1063,14 @@ static int coroutine_fn vpc_co_create(BlockdevCreateOptions *opts, } footer->timestamp = cpu_to_be32(time(NULL) - VHD_TIMESTAMP_BASE); - /* Version of Virtual PC 2007 */ - footer->major = cpu_to_be16(0x0005); - footer->minor = cpu_to_be16(0x0003); + if (vpc_opts->xenserver_compat) { + footer->major = cpu_to_be16(0x0001); + footer->minor = cpu_to_be16(0x0000); + } else { + /* Version of Virtual PC 2007 */ + footer->major = cpu_to_be16(0x0005); + footer->minor = cpu_to_be16(0x0003); + } footer->orig_size = cpu_to_be64(total_size); footer->current_size = cpu_to_be64(total_size); footer->cyls = cpu_to_be16(cyls); @@ -1101,6 +1111,7 @@ static int coroutine_fn vpc_co_create_opts(const char *filename, static const QDictRenames opt_renames[] = { { VPC_OPT_FORCE_SIZE, "force-size" }, + { VPC_OPT_XENSERVER_COMPAT, "xenserver-compat" }, { NULL, NULL }, }; @@ -1220,6 +1231,11 @@ static QemuOptsList vpc_create_opts = { "specified, rather than using the nearest CHS-based " "calculation" }, + { + .name = VPC_OPT_XENSERVER_COMPAT, + .type = QEMU_OPT_BOOL, + .help = "Set creator to tap" + }, { /* end of list */ } } }; diff --git a/qapi/block-core.json b/qapi/block-core.json index aa97ee2..68daa3c 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -4669,6 +4669,7 @@ # @force-size Force use of the exact byte size instead of rounding to the # next size that can be represented in CHS geometry # (default: false) +# @xenserver-compat Xenserver comapt # # Since: 2.12 ## @@ -4676,7 +4677,9 @@ 'data': { 'file': 'BlockdevRef', 'size': 'size', '*subformat': 'BlockdevVpcSubformat', - '*force-size': 'bool' } } + '*force-size': 'bool', + '*xenserver-compat': 'bool' + } } ## # @BlockdevCreateOptions: