Maria Kustova [Mon, 11 Aug 2014 10:34:00 +0000 (14:34 +0400)]
image-fuzzer: Fuzzing functions for qcow2 images
The fuzz submodule of the qcow2 image generator contains fuzzing functions for
image fields.
Each fuzzing function contains a list of constraints and a call of a helper
function that randomly selects a fuzzed value satisfied to one of constraints.
For now constraints include only known as invalid or potentially dangerous
values. But after investigation of code coverage by fuzz tests they will be
expanded by heuristic values based on inner checks and flows of a program
under test.
Now fuzzing of a header, header extensions and a backing file name is
supported.
Maria Kustova [Mon, 11 Aug 2014 10:33:59 +0000 (14:33 +0400)]
image-fuzzer: Tool for fuzz tests execution
The purpose of the test runner is to prepare the test environment (e.g. create
a work directory, a test image, etc), execute a program under test with
parameters, indicate a test failure if the program was killed during the test
execution and collect core dumps, logs and other test artifacts.
The test runner doesn't depend on an image format, so it can be used with any
external image generator.
[Fixed path to qcow2 format module "qcow2" instead of "../qcow2" since
runner.py is no longer in a sub-directory.
--Stefan]
Michael Tokarev [Wed, 13 Aug 2014 07:23:31 +0000 (11:23 +0400)]
ide: only constrain read/write requests to drive size, not other types
Commit 58ac321135a introduced a check to ide dma processing which
constrains all requests to drive size. However, apparently, some
valid requests (like TRIM) does not fit in this constraint, and
fails in 2.1. So check the range only for reads and writes.
Marc Marí [Tue, 12 Aug 2014 11:41:51 +0000 (13:41 +0200)]
virtio-blk: Correct bug in support for flexible descriptor layout
Without this correction, only a three descriptor layout is accepted, and
requests with just two descriptors are not completed and no error message is
displayed.
Parallels has released in the recent updates of Parallels Server 5/6
new addition to his image format. Images with signature WithouFreSpacExt
have offsets in the catalog coded not as offsets in sectors (multiple
of 512 bytes) but offsets coded in blocks (i.e. header->tracks * 512)
In this case all 64 bits of header->nb_sectors are used for image size.
This patch implements support of this for qemu-img and also adds specific
check for an incorrect image. Images with block size greater than
INT_MAX/513 are not supported. The biggest available Parallels image
cluster size in the field is 1 Mb. Thus this limit will not hurt
anyone.
parallels: split check for parallels format in parallels_open
and rework error path a bit. There is no difference at the moment, but
the code will be definitely shorter when additional processing will
be required for WithouFreSpacExt
parallels: extend parallels format header with actual data values
Parallels image format has several additional fields inside:
- nb_sectors is actually 64 bit wide. Upper 32bits are not used for
images with signature "WithoutFreeSpace" and must be explicitly
zeroed according to Parallels. They will be used for images with
signature "WithouFreSpacExt"
- inuse is magic which means that the image is currently opened for
read/write or was not closed correctly, the magic is 0x746f6e59
- data_off is the location of the first data block. It can be zero
and in this case data starts just beyond the header aligned to
512 bytes. Though this field does not matter for read-only driver
This patch adds these values to struct parallels_header and adds
proper handling of nb_sectors for currently supported WithoutFreeSpace
images.
The dataplane code is currently doing a hard exit if it fails to set
up either guest or host notifiers. In practice, this may mean that a
guest suddenly dies after a dataplane device failed to come up (e.g.,
when a file descriptor limit is hit for tne nth device).
Let's just try to unwind the setup instead and return.
Gonglei [Mon, 11 Aug 2014 09:34:21 +0000 (17:34 +0800)]
channel-posix: using qemu_set_nonblock() instead of fcntl(O_NONBLOCK)
Technically, fcntl(soc, F_SETFL, O_NONBLOCK)
is incorrect since it clobbers all other file flags.
We can use F_GETFL to get the current flags, set or
clear the O_NONBLOCK flag, then use F_SETFL to set the flags.
Gonglei [Mon, 11 Aug 2014 09:34:20 +0000 (17:34 +0800)]
qemu-char: using qemu_set_nonblock() instead of fcntl(O_NONBLOCK)
Technically, fcntl(soc, F_SETFL, O_NONBLOCK)
is incorrect since it clobbers all other file flags.
We can use F_GETFL to get the current flags, set or
clear the O_NONBLOCK flag, then use F_SETFL to set the flags.
cmd646: synchronise DMA interrupt status with UDMA interrupt status
Make sure that the standard DMA interrupt status bits reflect any changes made
to the UDMA interrupt status bits. The CMD646U2 datasheet claims that these
bits are equivalent, and they must be synchronised for guests that manipulate
both registers.
John Snow [Mon, 4 Aug 2014 21:11:25 +0000 (17:11 -0400)]
qtest/ide: Fix small memory leak
For libqos debugging purposes, it's nice to
be able to assert that tests and associated libraries
have no memory leaks. To that end, free up the
trivial cmdline leak.
The remaining leaks caused by pc_alloc_init are fixed
instead by my first-fit pc_alloc implementation already
on the qemu-devel mailing list.
John Snow [Mon, 4 Aug 2014 21:11:24 +0000 (17:11 -0400)]
libqos: allow qpci_iomap to return BAR mapping size
This patch allows qpci_iomap to return the size of the
BAR mapping that it created, to allow driver applications
(e.g, ahci-test) to make determinations about the suitability
or the mapping size, or in the specific case of AHCI, how
many ports are supported by the HBA.
John Snow [Mon, 4 Aug 2014 21:11:23 +0000 (17:11 -0400)]
libqos: Fixes a small memory leak.
Allow users the chance to clean up the QPCIBusPC structure
by adding a small cleanup routine. Helps clear up small
memory leaks during setup/teardown, to allow for cleaner
debug output messages.
John Snow [Mon, 4 Aug 2014 21:11:22 +0000 (17:11 -0400)]
libqtest: Correct small memory leak.
Fixes a small memory leak inside of libqtest.
After we produce a test path and glib copies the string
for itself, we should clean up our temporary copy.
John Snow [Mon, 4 Aug 2014 21:11:20 +0000 (17:11 -0400)]
qtest: Adding qtest_memset and qmemset.
Currently, libqtest allows for memread and memwrite, but
does not offer a simple way to zero out regions of memory.
This patch adds a simple function to do so.
Paolo Bonzini [Mon, 4 Aug 2014 21:11:18 +0000 (17:11 -0400)]
ahci: construct PIO Setup FIS for PIO commands
PIO commands should put a PIO Setup FIS in the receive area when data
transfer ends. Currently QEMU does not do this and only places the
D2H FIS at the end of the operation.
Paolo Bonzini [Mon, 4 Aug 2014 21:11:17 +0000 (17:11 -0400)]
ide: make all commands go through cmd_done
AHCI has code to fill in the D2H FIS trigger the IRQ all over the place.
Centralize this in a single cmd_done callback by generalizing the existing
async_cmd_done callback.
Paolo Bonzini [Mon, 4 Aug 2014 21:11:11 +0000 (17:11 -0400)]
ide: remove wrong setting of BM_STATUS_INT
Similar to the case removed in commit 69c38b8 (ide/core: Remove explicit
setting of BM_STATUS_INT, 2011-05-19), the only remaining use of
add_status(..., BM_STATUS_INT) is for short PRDs. The flag should
not be raised in this case.
Peter Maydell [Fri, 15 Aug 2014 13:49:50 +0000 (14:49 +0100)]
Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
Block patches
# gpg: Signature made Fri 15 Aug 2014 14:07:42 BST using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <[email protected]>"
* remotes/kevin/tags/for-upstream: (59 commits)
block: Catch !bs->drv in bdrv_check()
iotests: Add test for image header overlap
qcow2: Catch !*host_offset for data allocation
qcow2: Return useful error code in refcount_init()
mirror: Handle failure for potentially large allocations
vpc: Handle failure for potentially large allocations
vmdk: Handle failure for potentially large allocations
vhdx: Handle failure for potentially large allocations
vdi: Handle failure for potentially large allocations
rbd: Handle failure for potentially large allocations
raw-win32: Handle failure for potentially large allocations
raw-posix: Handle failure for potentially large allocations
qed: Handle failure for potentially large allocations
qcow2: Handle failure for potentially large allocations
qcow1: Handle failure for potentially large allocations
parallels: Handle failure for potentially large allocations
nfs: Handle failure for potentially large allocations
iscsi: Handle failure for potentially large allocations
dmg: Handle failure for potentially large allocations
curl: Handle failure for potentially large allocations
...
Max Reitz [Thu, 7 Aug 2014 20:47:55 +0000 (22:47 +0200)]
block: Catch !bs->drv in bdrv_check()
qemu-img check calls bdrv_check() twice if the first run repaired some
inconsistencies. If the first run however again triggered corruption
prevention (on qcow2) due to very bad inconsistencies, bs->drv may be
NULL afterwards. Thus, bdrv_check() should check whether bs->drv is set.
Max Reitz [Thu, 7 Aug 2014 20:47:53 +0000 (22:47 +0200)]
qcow2: Catch !*host_offset for data allocation
qcow2_alloc_cluster_offset() uses host_offset == 0 as "no preferred
offset" for the (data) cluster range to be allocated. However, this
offset is actually valid and may be allocated on images with a corrupted
refcount table or first refcount block.
In this case, the corruption prevention should normally catch that
write anyway (because it would overwrite the image header). But since 0
is a special value here, the function assumes that nothing has been
allocated at all which it asserts against.
Because this condition is not qemu's fault but rather that of a broken
image, it shouldn't throw an assertion but rather mark the image corrupt
and show an appropriate message, which this patch does by calling the
corruption check earlier than it would be called normally (before the
assertion).
Max Reitz [Wed, 28 May 2014 22:19:54 +0000 (00:19 +0200)]
qcow2: Return useful error code in refcount_init()
If bdrv_pread() returns an error, it is very unlikely that it was
ENOMEM. In this case, the return value should be passed along; as
bdrv_pread() will always either return the number of bytes read or a
negative value (the error code), the condition for checking whether
bdrv_pread() failed can be simplified (and clarified) as well.
Kevin Wolf [Wed, 21 May 2014 16:16:21 +0000 (18:16 +0200)]
mirror: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the mirror block job.
Kevin Wolf [Wed, 21 May 2014 16:08:38 +0000 (18:08 +0200)]
vpc: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the vpc block driver.
Kevin Wolf [Tue, 20 May 2014 11:56:27 +0000 (13:56 +0200)]
vmdk: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the vmdk block driver.
Kevin Wolf [Tue, 20 May 2014 11:55:50 +0000 (13:55 +0200)]
vhdx: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the vhdx block driver.
Kevin Wolf [Tue, 20 May 2014 11:25:43 +0000 (13:25 +0200)]
vdi: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the vdi block driver.
Kevin Wolf [Wed, 21 May 2014 16:11:48 +0000 (18:11 +0200)]
rbd: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the rbd block driver.
Kevin Wolf [Wed, 21 May 2014 16:05:47 +0000 (18:05 +0200)]
raw-win32: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the raw-win32 block driver.
Kevin Wolf [Wed, 21 May 2014 16:02:42 +0000 (18:02 +0200)]
raw-posix: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the raw-posix block driver.
Kevin Wolf [Tue, 20 May 2014 11:39:57 +0000 (13:39 +0200)]
qed: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the qed block driver.
Kevin Wolf [Tue, 20 May 2014 15:12:47 +0000 (17:12 +0200)]
qcow2: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the qcow2 block driver.
Kevin Wolf [Tue, 20 May 2014 11:36:05 +0000 (13:36 +0200)]
qcow1: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the qcow1 block driver.
Kevin Wolf [Tue, 20 May 2014 11:32:14 +0000 (13:32 +0200)]
parallels: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the parallels block driver.
Kevin Wolf [Tue, 20 May 2014 11:31:20 +0000 (13:31 +0200)]
nfs: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the nfs block driver.
Kevin Wolf [Tue, 20 May 2014 11:30:49 +0000 (13:30 +0200)]
iscsi: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the iscsi block driver.
Kevin Wolf [Tue, 20 May 2014 11:28:14 +0000 (13:28 +0200)]
dmg: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the dmg block driver.
Kevin Wolf [Tue, 20 May 2014 11:26:40 +0000 (13:26 +0200)]
curl: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the curl block driver.
Kevin Wolf [Tue, 20 May 2014 11:22:38 +0000 (13:22 +0200)]
cloop: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the cloop block driver.
Kevin Wolf [Tue, 20 May 2014 11:21:26 +0000 (13:21 +0200)]
bochs: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses the allocations in the bochs block driver.
Kevin Wolf [Tue, 20 May 2014 11:16:51 +0000 (13:16 +0200)]
block: Handle failure for potentially large allocations
Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.
This patch addresses bounce buffer allocations in block.c. While at it,
convert bdrv_commit() from plain g_malloc() to qemu_try_blockalign().
Jeff Cody [Wed, 23 Jul 2014 21:23:00 +0000 (17:23 -0400)]
block: vpc - use block layer ops in vpc_create, instead of posix calls
Use the block layer to create, and write to, the image file in the VPC
.bdrv_create() operation.
This has a couple of benefits: Images can now be created over protocols,
and hacks such as NOCOW are not needed in the image format driver, and
the underlying file protocol appropriate for the host OS can be relied
upon.
Jeff Cody [Wed, 23 Jul 2014 21:22:59 +0000 (17:22 -0400)]
block: use the standard 'ret' instead of 'result'
Most QEMU code uses 'ret' for function return values. The VDI driver
uses a mix of 'result' and 'ret'. This cleans that up, switching over
to the standard 'ret' usage.
Jeff Cody [Wed, 23 Jul 2014 21:22:58 +0000 (17:22 -0400)]
block: vdi - use block layer ops in vdi_create, instead of posix calls
Use the block layer to create, and write to, the image file in the
VDI .bdrv_create() operation.
This has a couple of benefits: Images can now be created over protocols,
and hacks such as NOCOW are not needed in the image format driver, and
the underlying file protocol appropriate for the host OS can be relied
upon.
Jeff Cody [Wed, 23 Jul 2014 21:22:57 +0000 (17:22 -0400)]
block: allow bdrv_unref() to be passed NULL pointers
If bdrv_unref() is passed a NULL BDS pointer, it is safe to
exit with no operation. This will allow cleanup code to blindly
call bdrv_unref() on a BDS that has been initialized to NULL.
Paolo Bonzini [Wed, 6 Aug 2014 09:33:41 +0000 (11:33 +0200)]
test-coroutine: add baseline test that times the cost of function calls
This can be used to compute the cost of coroutine operations. In the
end the cost of the function call is a few clock cycles, so it's pretty
cheap for now, but it may become more relevant as the coroutine code
is optimized.
For example, here are the results on my machine:
Function call 100000000 iterations: 0.173884 s
Yield 100000000 iterations: 8.445064 s
Lifecycle 1000000 iterations: 0.098445 s
Nesting 10000 iterations of 1000 depth each: 7.406431 s
One yield takes 83 nanoseconds, one enter takes 97 nanoseconds,
one coroutine allocation takes (roughly, since some of the allocations
in the nesting test do hit the pool) 739 nanoseconds:
Jeff Cody [Wed, 6 Aug 2014 19:54:58 +0000 (15:54 -0400)]
block: VHDX endian fixes
This patch contains several changes for endian conversion fixes for
VHDX, particularly for big-endian machines (multibyte values in VHDX are
all on disk in LE format).
Tests were done with existing qemu-iotests on an IBM POWER7 (8406-71Y).
This includes sample images created by Hyper-V, both with dirty logs and
without.
In addition, VHDX image files created (and written to) on a BE machine
were tested on a LE machine, and vice-versa.
Stefan Hajnoczi [Tue, 15 Jul 2014 14:44:26 +0000 (16:44 +0200)]
thread-pool: avoid deadlock in nested aio_poll() calls
The thread pool has a race condition if two elements complete before
thread_pool_completion_bh() runs:
If element A's callback waits for element B using aio_poll() it will
deadlock since pool->completion_bh is not marked scheduled when the
nested aio_poll() runs.
Fix this by marking the BH scheduled while thread_pool_completion_bh()
is executing. This way any nested aio_poll() loops will enter
thread_pool_completion_bh() and complete the remaining elements.
Stefan Hajnoczi [Tue, 15 Jul 2014 14:44:25 +0000 (16:44 +0200)]
thread-pool: avoid per-thread-pool EventNotifier
EventNotifier is implemented using an eventfd or pipe. It therefore
consumes file descriptors, which can be limited by rlimits and should
therefore be used sparingly.
Switch from EventNotifier to QEMUBH in thread-pool.c. Originally
EventNotifier was used because qemu_bh_schedule() was not thread-safe
yet.
Stefan Hajnoczi [Mon, 7 Jul 2014 13:15:53 +0000 (15:15 +0200)]
block: bump coroutine pool size for drives
When a BlockDriverState is associated with a storage controller
DeviceState we expect guest I/O. Use this opportunity to bump the
coroutine pool size by 64.
This patch ensures that the coroutine pool size scales with the number
of drives attached to the guest. It should increase coroutine pool
usage (which makes qemu_coroutine_create() fast) without hogging too
much memory when fewer drives are attached.
@mport: #'mport' is the port number on which mapperd is
listening. This is optional and if not specified,
QEMU will make Archipelago to use the default port.
@vport: #'vport' is the port number on which vlmcd is
listening. This is optional and if not specified,
QEMU will make Archipelago to use the default port.
@segment: #optional The name of the shared memory segment
Archipelago stack is using. This is optional
and if not specified, QEMU will make Archipelago
use the default value, 'archipelago'.
'mport' is the port number on which mapperd is listening. This is optional
and if not specified, QEMU will make Archipelago to use the default port.
'vport' is the port number on which vlmcd is listening. This is optional
and if not specified, QEMU will make Archipelago to use the default port.
'segment' is the name of the shared memory segment Archipelago stack is using.
This is optional and if not specified, QEMU will make Archipelago to use the
default value, 'archipelago'.
This drops the unnecessary bdrv_truncate() from, and also improves,
cluster allocation code path.
Before, when we need a new cluster, get_cluster_offset truncates the
image to bdrv_getlength() + cluster_size, and returns the offset of
added area, i.e. the image length before truncating.
This is not efficient, so it's now rewritten as:
- Save the extent file length when opening.
- When allocating cluster, use the saved length as cluster offset.
- Don't truncate image, because we'll anyway write data there: just
write any data at the EOF position, in descending priority:
* New user data (cluster allocation happens in a write request).
* Filling data in the beginning and/or ending of the new cluster, if
not covered by user data: either backing file content (COW), or
zero for standalone images.
One major benifit of this change is, on host mounted NFS images, even
over a fast network, ftruncate is slow (see the example below). This
change significantly speeds up cluster allocation. Comparing by
converting a cirros image (296M) to VMDK on an NFS mount point, over
1Gbe LAN:
$ time qemu-img convert cirros-0.3.1.img /mnt/a.raw -O vmdk
Before:
real 0m21.796s
user 0m0.130s
sys 0m0.483s
After:
real 0m2.017s
user 0m0.047s
sys 0m0.190s
We also get rid of unchecked bdrv_getlength() and bdrv_truncate(), and
get a little more documentation in function comments.
Tested that this passes qemu-iotests for all VMDK subformats.
qemu-iotests: Add data pattern in version3 VMDK sample image in 059
It's possible that we diverge from the specification with our
implementation. Having a reference image in the test cases may detect
such problems when we introduce a bug that can read what it creates, but
can't handle a real VMDK.
Stefan Hajnoczi [Wed, 9 Jul 2014 12:01:32 +0000 (14:01 +0200)]
qdev-monitor: include QOM properties in -device FOO, help output
Update -device FOO,help to include QOM properties in addition to qdev
properties. Devices are gradually adding more QOM properties that are
not reflected as qdev properties.
It is important to report all device properties since management tools
like libvirt use this information (and device-list-properties QMP) to
detect the presence of QEMU features.
This patch reuses the device-list-properties QMP machinery to avoid code
duplication.
Stefan Hajnoczi [Wed, 9 Jul 2014 12:01:31 +0000 (14:01 +0200)]
qmp: hide "hotplugged" device property from device-list-properties
The "hotplugged" device property was not reported before commit f4eb32b590bf58c1c67570775eb78beb09964fad ("qmp: show QOM properties in
device-list-properties"). Fix this difference.
Stefan Hajnoczi [Wed, 23 Jul 2014 11:55:32 +0000 (12:55 +0100)]
docs/multiple-iothreads.txt: add documentation on IOThread programming
This document explains how IOThreads and the main loop are related,
especially how to write code that can run in an IOThread. Currently
only virtio-blk-data-plane uses these techniques. The next obvious
target is virtio-scsi; there has also been work on virtio-net.
Maria Kustova [Mon, 21 Jul 2014 11:16:33 +0000 (15:16 +0400)]
docs: Make the recommendation for the backing file name position a requirement
The current version of the qcow2 specification recommends to save the backing
file name in the end of the first cluster. It follows that the backing file
name can be saved somewhere in the image, but the first cluster, which
contradicts the current QEMU implementation.
The patch makes the backing file name required to be placed after the header
extensions in the first image cluster.
projects / qemu.git / log