Inactive images generally request less permissions for their image files
than they would if they were active (in particular, write permissions).
Activating the image involves extending the permissions, therefore.

drv->bdrv_invalidate_cache() can already require write access to the
image file, so we have to update the permissions earlier than that.
The current code does it only later, so we have to move up this part.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

After committing the qcow2 image contents into the base image, qemu-img
will call bdrv_make_empty to drop the payload in the layered image.

When this is done for qcow2 images, it blows away the LUKS encryption
header, making the resulting image unusable. There are two codepaths
for emptying a qcow2 image, and the second (slower) codepath leaves
the LUKS header intact, so force use of that codepath.
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

bdrv_set_read_only() is used by some block drivers to override the
read-only option given by the user. This is not how read-only images
generally work in QEMU: Instead of second guessing what the user really
meant (which currently includes making an image read-only even if the
user didn't only use the default, but explicitly said read-only=off), we
should error out if we can't provide what the user requested.

This adds deprecation warnings to all callers of bdrv_set_read_only() so
that the behaviour can be corrected after the usual deprecation period.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Currently if trying to change encryption parameters on a qcow2 image, qemu-img
will abort. We already explicitly check for attempt to change encrypt.format
but missed other parameters like encrypt.key-secret. Rather than list each
parameter, just blacklist changing of all parameters with a 'encrypt.' prefix.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

error_setg_errno() takes a positive errno code. Spotted by Coverity
(CID 1381628).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

This avoids that random UI frontend error messages end up in the output.
In particular, we were seeing this line in CI error logs:

+Unable to init server: Could not connect: Connection refused
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NKashyap Chamarthy <kchamart@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>

replication_child_perm request write
permissions for all child which will lead bdrv_check_perm fail.
replication_child_perm() should request write
permissions only if it is writable itself.
Signed-off-by: NWang Guang <wang.guang55@zte.com.cn>
Signed-off-by: NWang Yong <wang.yong155@zte.com.cn>
Reviewed-by: NXie Changlong <xiechanglong@cmss.chinamobile.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

sdl2 fixes for 2.11

# gpg: Signature made Fri 17 Nov 2017 10:06:27 GMT
# gpg:                using RSA key 0x4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20171117-pull-request:
  sdl2: Fix broken display updating after the window is hidden
  sdl2: Do not leave grab when fullscreen
  sdl2: Fix dead keyboard after fullsceen
  sdl2: Use the same pointer show/hide logic for absolute and relative mode
  sdl2: Do not quit the emulator when an auxilliary window is closed
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

pc, pci, virtio: fixes for rc1

A bunch of fixes all over the place.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Thu 16 Nov 2017 16:37:21 GMT
# gpg:                using RSA key 0x281F0DB8D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"
# Primary key fingerprint: 0270 606B 6F3C DF3D 0B17  0970 C350 3912 AFBE 8E67
#      Subkey fingerprint: 5D09 FD08 71C8 F85B 94CA  8A0D 281F 0DB8 D28D 5469

* remotes/mst/tags/for_upstream:
  tests/bios-tables-test: Fix endianess problems when passing data to iasl
  build-sys: restrict vmcoreinfo to fw_cfg+dma capable targets
  vmcoreinfo: put it in the 'misc' device category
  NUMA: Enable adding NUMA node implicitly
  tests/acpi-test-data: update _CRS in DSDT
  hw/pcie-pci-bridge: restrict to X86 and ARM
  hw/pci-host: Fix x86 Host Bridges 64bit PCI hole
  pci: Initialize pci_dev->name before use
  fix: unrealize virtio device if we fail to hotplug it
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

# gpg: Signature made Thu 16 Nov 2017 16:36:02 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  throttle-groups: forget timer and schedule next TGM on detach
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

The bios-tables-test was writing out files that we pass to iasl in
with the wrong endianness in the header when running on a big endian
host. So instead of storing mixed endian information in our structures,
let's keep everything in little endian and byte-swap it only when we
need a value in the code.
Reported-by: NDaniel P. Berrange <berrange@redhat.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1724570Suggested-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Tested-by: N"Daniel P. Berrange" <berrange@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

vmcoreinfo is built for all targets. However, it requires fw_cfg with
DMA operations support (write operation). Restrict vmcoreinfo exposure
to architectures that are supporting FW_CFG_DMA, that is arm-virt and
x86 only atm.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NDaniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Tested-by: NDaniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Linux and Windows need ACPI SRAT table to make memory hotplug work properly,
however currently QEMU doesn't create SRAT table if numa options aren't present
on CLI.

Which breaks both linux and windows guests in certain conditions:
 * Windows: won't enable memory hotplug without SRAT table at all
 * Linux: if QEMU is started with initial memory all below 4Gb and no SRAT table
   present, guest kernel will use nommu DMA ops, which breaks 32bit hw drivers
   when memory is hotplugged and guest tries to use it with that drivers.

Fix above issues by automatically creating a numa node when QEMU is started with
memory hotplug enabled but without '-numa' options on CLI.
(PS: auto-create numa node only for new machine types so not to break migration).

Which would provide SRAT table to guests without explicit -numa options on CLI
and would allow:
 * Windows: to enable memory hotplug
 * Linux: switch to SWIOTLB DMA ops, to bounce DMA transfers to 32bit allocated
   buffers that legacy drivers/hw can handle.

[Rewritten by Igor]
Reported-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Suggested-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NDou Liyang <douly.fnst@cn.fujitsu.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Alistair Francis <alistair23@gmail.com>
Cc: Takao Indoh <indou.takao@jp.fujitsu.com>
Cc: Izumi Taku <izumi.taku@jp.fujitsu.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

commit dadf988e81b15065ac1d6dbaf4b87b5b80c7b670
    hw/pci-host: Fix x86 Host Bridges 64bit PCI hole

Added a 64 bit hole to _CRS of PCI0.
Update the expected files accordingly.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

The PCIE-PCI bridge is specific to "pure" PCIe systems
(on QEMU we have X86 and ARM), it does not make sense to
have it in other archs.
Reported-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NMarcel Apfelbaum <marcel@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Tested-by: NYongbok Kim <yongbok.kim@mips.com>

Currently there is no MMIO range over 4G
reserved for PCI hotplug. Since the 32bit PCI hole
depends on the number of cold-plugged PCI devices
and other factors, it is very possible is too small
to hotplug PCI devices with large BARs.

Fix it by reserving 2G for I4400FX chipset
in order to comply with older Win32 Guest OSes
and 32G for Q35 chipset.

Even if the new defaults of pci-hole64-size will appear in
"info qtree" also for older machines, the property was
not implemented so no changes will be visible to guests.

Note this is a regression since prev QEMU versions had
some range reserved for 64bit PCI hotplug.
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NMarcel Apfelbaum <marcel@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

This moves pci_dev->name initialization earlier so
pci_dev->bus_master_as could get a name instead of an empty string.
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

If we fail to hotplug virtio-blk device and then suspend
or shutdown VM, qemu is likely to crash.

Re-production steps:
1. Run VM named vm001
2. Create a virtio-blk.xml which contains wrong configurations:
<disk device="lun" rawio="yes" type="block">
  <driver cache="none" io="native" name="qemu" type="raw" />
  <source dev="/dev/mapper/11-dm" />
  <target bus="virtio" dev="vdx" />
</disk>
3. Run command : virsh attach-device vm001 virtio-blk.xml
error: Failed to attach device from blk-scsi.xml
error: internal error: unable to execute QEMU command 'device_add': Please set scsi=off for virtio-blk devices in order to use virtio 1.0
it means hotplug virtio-blk device failed.
4. Suspend or shutdown VM will leads to qemu crash

Problem happens in virtio_vmstate_change which is called by
vm_state_notify:
vdev’s parent_bus is NULL, so qdev_get_parent_bus(DEVICE(vdev)) will crash.
virtio_vmstate_change is added to the list vm_change_state_head at virtio_blk_device_realize(virtio_init),
but after hotplug virtio-blk failed, virtio_vmstate_change will not be removed from vm_change_state_head.
Adding unrealize function of virtio-blk device can solve this problem.
Signed-off-by: Nlinzhecheng <linzhecheng@huawei.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Miscellaneous bugfixes

# gpg: Signature made Wed 15 Nov 2017 15:27:25 GMT
# gpg:                using RSA key 0xBFFBD25F78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream:
  fix scripts/update-linux-headers.sh here document
  exec: Do not resolve subpage in mru_section
  util/stats64: Fix min/max comparisons
  cpu-exec: avoid cpu_exec_nocache infinite loop with record/replay
  cpu-exec: don't overwrite exception_index
  vhost-user-scsi: add missing virtqueue_size param
  target-i386: adds PV_TLB_FLUSH CPUID feature bit
  thread-posix: fix qemu_rec_mutex_trylock macro
  Makefile: simpler/faster "make help"
  ioapic/tracing: Remove last DPRINTFs
  Enable 8-byte wide MMIO for 16550 serial devices
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

tg->any_timer_armed[] must be cleared when detaching pending timers from
the AioContext.  Failure to do so leads to hung I/O because it looks
like there are still timers pending when in fact they have been removed.

Other ThrottleGroupMembers might have requests pending too so it's
necessary to schedule the next TGM so it can set a timer.

This patch fixes hung I/O when QEMU is launched with drives that are in
the same throttling group:

  (guest)$ dd if=/dev/zero of=/dev/vdb oflag=direct bs=512 &
  (guest)$ dd if=/dev/zero of=/dev/vdc oflag=direct bs=512 &
  (qemu) stop
  (qemu) cont
  ...I/O is stuck...
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20171116112150.27607-1-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

User-mode memory helper fixes

# gpg: Signature made Wed 15 Nov 2017 12:32:33 GMT
# gpg:                using RSA key 0x64DF38E8AF7E215F
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>"
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-tcg-20171115:
  target/arm: Fix GETPC usage in do_paired_cmpxchg64_l/be
  target/arm: Use helper_retaddr in stxp helpers
  tcg: Record code_gen_buffer address for user-only memory helpers
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Merge tpm 2017/11/15 v1

# gpg: Signature made Wed 15 Nov 2017 11:51:47 GMT
# gpg:                using RSA key 0x75AD65802A0B4211
# gpg: Good signature from "Stefan Berger <stefanb@linux.vnet.ibm.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: B818 B9CA DF90 89C2 D5CE  C66B 75AD 6580 2A0B 4211

* remotes/stefanberger/tags/pull-tpm-2017-11-15-1:
  tpm_tis: Return 0 for every register in case of failure mode
  tpm_tis: Return TPM_VERSION_UNSPEC in case of BE failure
  tpm-emulator: protect concurrent ctrl_chr access
  specs: Extend TPM spec with TPM emulator description
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

With SDL 2.0.6, calling SDL_ShowWindow during SDL_WINDOWEVENT_HIDDEN
blocks all subsequent display updates.

Instead of trying to override the change, just update the scon->hidden
flag.
Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Message-Id: <20171112193032.9724-2-makovick@gmail.com>

This is a partial revert of d3f3a0f4,
which in turn is a workaround for a SDL bug.  The bug is fixed in 2.0.6,
see https://bugzilla.libsdl.org/show_bug.cgi?id=3410Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Prevents displaying of a doubled mouse pointer when moving the pointer
to the screen edges when fullscreen.
Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Message-Id: <20171112193032.9724-8-makovick@gmail.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Message-Id: <20171112193032.9724-7-makovick@gmail.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Also use a proper enum parameter for SDL_ShowCursor
Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Message-Id: <20171112193032.9724-4-makovick@gmail.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Message-Id: <20171112193032.9724-3-makovick@gmail.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

The minus sign after << causes the shell to strip only
preceding tabs, not spaces.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Message-Id: <20171110090354.29608-1-kraxel@redhat.com>
Fixes: 40bf8e9aReviewed-by: NRoman Kagan <rkagan@virtuozzo.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Tested-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This fixes a crash caused by picking the wrong memory region in
address_space_lookup_region seen with client code accessing a device
model that uses alias memory regions.  The expensive part of
address_space_lookup_region anyway is phys_page_find; performance-wise
it is okay to repeat the subsequent subpage lookup.
Signed-off-by: NBALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <20171114225941.072707456B5@zero.eik.bme.hu>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Rather than returning ~0, return 0 for every register in case of failure
mode. The '0' is better to indicate that there's no device there. It avoids
SeaBIOS detecting a device and getting stuck on it trying to read and write
its registers.
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>

In case the backend has a failure, such as the tpm_emulator's CMD_INIT
failing, the TIS goes into failure mode and does not respond to reads
or writes to MMIO registers. In this case we need to prevent the ACPI
table from being added and the straight-forward way is to indicate that
there's no known TPM version being used.
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>

The control chardev is being used from the data thread to set the
locality of the next request. Altough the chr has a write mutex, we
may potentially read the reply from another thread request.

Add a mutex to protect from concurrent control commands.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>

Following the recent extension of QEMU with a TPM emulator device,
update the specs describing for how to interact with the device.

The results of commands run inside a Linux VM are expected to be
similar to those when the TPM passthrough device is used, so we
just reuse that.
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>

Use of GETPC must be restricted to those functions that are
directly called from TCG generated code.
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Fixes: 2399d4e7Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

We use raw memory primitives along the !parallel_cpus paths in order to
simplify the endianness handling.  Because of that, we did not benefit
from the generic changes to cpu_ldst_user_only_template.h.

The simplest fix is to manipulate helper_retaddr here.
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

When we handle a signal from a fault within a user-only memory helper,
we cannot cpu_restore_state with the PC found within the signal frame.
Use a TLS variable, helper_retaddr, to record the unwind start point
to find the faulting guest insn.
Tested-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

stat64_min_slow() and stat64_max_slow() compare the wrong way.  This
makes iotest 136 fail with clang and -m32.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-Id: <20171114232223.25207-1-mreitz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Block patches for 2.11.0-rc1

# gpg: Signature made Tue 14 Nov 2017 17:22:17 GMT
# gpg:                using RSA key 0xF407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2017-11-14:
  qemu-iotests: update unsupported image formats in 194
  block/parallels: add migration blocker
  block/parallels: Do not update header or truncate image when INMIGRATE
  block/vhdx.c: Don't blindly update the header
  iotests: 077: Filter out 'resume' lines
  block/snapshot: dirty all dirty bitmaps on snapshot-switch
  qcow2: Check that corrupted images can be repaired in iotest 060
  iotests: Use new-style NBD connections
  iotests: Make 136 less flaky
  iotests: Make 083 less flaky
  iotests: Make 055 less flaky
  iotests: Add missing 'blkdebug::' in 040
  iotests: Make 030 less flaky
  qcow2: Assert that the crypto header does not overlap other metadata
  qcow2: Add iotest for an empty refcount table
  qcow2: Add iotest for an image with header.refcount_table_offset == 0
  qcow2: Don't open images with header.refcount_table_clusters == 0
  qcow2: Prevent allocating compressed clusters at offset 0
  qcow2: Prevent allocating L2 tables at offset 0
  qcow2: Prevent allocating refcount blocks at offset 0
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>