The deprecation of features in QEMU is totally adhoc currently,
with no way for the user to get a list of what is deprecated
in each release. This adds an appendix to the doc that records
when each deprecation was made and provides text explaining
what to use instead, if anything.
Since there has been no formal policy around removal of deprecated
features in the past, any deprecations prior to 2.10.0 are to be
treated as if they had been made at the 2.10.0 release. Thus the
earliest that existing deprecations will be deleted is the start
of the 2.12.0 cycle.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20170725113638.7019-1-berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Expand the image format docs to cover the new options for
the qcow, qcow2 and luks disk image formats
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170623162419.26068-21-berrange@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
Since commit 3f2ce724f1 ("Move the qemu-ga description into a
separate chapter"), the qemu.1 man page looks pretty much screwed
up, e.g. the title was "qemu-ga - QEMU Guest Agent" instead of
"qemu-doc - QEMU Emulator User Documentation". However, that movement
of the gemu-ga chapter is not the real problem, it just triggered
another bug in the qemu-doc.texi: There are some parts in the file
which introduce a "@c man begin OPTIONS" section, but never close
it again with "@c man end". After adding the proper end tags here,
the title of the man page is right again and the previously wrongly
tagged sections now also show up correctly in the man page, too.
Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1497863771-24929-1-git-send-email-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a link to the GPLv2 and a link to the LICENSE file in the
QEMU repository to fix the two TODO items in this appendix.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
The qemu-ga description is currently a subsection of the Disk Images
chapter - which does not make much sense since the qemu-ga is not
directly related to disk images. So let's move this information
into a separate chapter instead.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
The preferred way of adding USB devices is via "-device" and
"device_add" nowadays, so let's start to get rid of "-usbdevice"
and "usb_add" in the documentation. While we're at it, also
add the new USB devices there which have been added to QEMU
during the last years, and get rid of the old "vendorid" and
"productid" parameters of "-usbdevice serial" which have been
removed in QEMU version 0.14.0 already.
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1494256429-31720-1-git-send-email-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
There are some broken URLs in the qemu-doc which reference tools that
are not available at their original location anymore. Fortunately, they
have been mirrored to archive.org, so point to that location instead.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
RFC 6331 documents a number of serious security weaknesses in
the SASL DIGEST-MD5 mechanism. As such, QEMU should not be
using or recommending it as a default mechanism for VNC auth
with SASL.
GSSAPI (Kerberos) is the only other viable SASL mechanism that
can provide secure session encryption so enable that by defalt
as the replacement. If users have TLS enabled for VNC, they can
optionally decide to use SCRAM-SHA-1 instead of GSSAPI, allowing
plain username and password auth.
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Add remaining bits of the Altera NiosII R1 support into qemu, which
is documentation, MAINTAINERS file entry, configure bits, arch_init
and configuration files for both linux-user (userland binaries) and
softmmu (hardware emulation).
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chris Wulff <crwulff@gmail.com>
Cc: Jeff Da Silva <jdasilva@altera.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Sandra Loosemore <sandra@codesourcery.com>
Cc: Yves Vandervennet <yvanderv@altera.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Message-Id: <20170118220146.489-8-marex@denx.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Remove the Niagara stub implementation from sun4u.c and add a machine,
compatible with Legion simulator from the OpenSPARC T1 project.
The machine uses the firmware supplied with the OpenSPARC T1 project,
http://download.oracle.com/technetwork/systems/opensparc/OpenSPARCT1_Arch.1.5.tar.bz2
in the directory S10image/, and is able to boot the supplied Solaris 10 image.
Note that for compatibility with the naming conventions for SPARC machines
the new machine name is lowercase niagara.
Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Document:
1. The new debug and logfile options with their usages
2. New json format and its usage and
3. update "GlusterFS, Device URL Syntax" section in "Invocation"
Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Merge what is left of qemu-tech into the main manual as an appendix.
Ultimately we should have a new internals manual built from docs/, and
then the "Translator Internals" parts of qemu-tech could move to docs/
as well. The bits on limitation and features of CPU emulation should
remain in qemu-doc.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
These are interesting for users too, since nowadays most
qemu-user users are going to be somewhat technical rather than
just people that want to run Wine. Some detail is lost, on
the other hand some of the information I removed (e.g. basic
block unchaining) was obsolete.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
These are in README or obsolete, and the detailed version can be on a
website instead.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The user manual has an obsolete introduction, and the one in
the internals manual lists QEMU's features quite nicely.
Drop the obsolete content and remove generic user-level
documentation from qemu-tech.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Vmdk images have metadata to indicate the vmware virtual
hardware version image was created/tested to run with.
Allow users to specify that version via new 'hwversion'
option.
[ kwolf: Adjust qemu-iotests common.filter ]
Signed-off-by: Janne Karhunen <Janne.Karhunen@gmail.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Migration with ivshmem needs to be carefully orchestrated to work.
Exactly one peer (the "master") migrates to the destination, all other
peers need to unplug (and disconnect), migrate, plug back (and
reconnect). This is sort of documented in qemu-doc.
If peers connect on the destination before migration completes, the
shared memory can get messed up. This isn't documented anywhere. Fix
that in qemu-doc.
To avoid messing up register IVPosition on migration, the server must
assign the same ID on source and destination. ivshmem-spec.txt leaves
ID assignment unspecified, however.
Amend ivshmem-spec.txt to require the first client to receive ID zero.
The example ivshmem-server complies: it always assigns the first
unused ID.
For a bit of additional safety, enforce ID zero for the master. This
does nothing when we're not using a server, because the ID is zero for
all peers then.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-40-git-send-email-armbru@redhat.com>
ivshmem can be configured with and without interrupt capability
(a.k.a. "doorbell"). The two configurations have largely disjoint
options, which makes for a confusing (and badly checked) user
interface. Moreover, the device can't tell the guest whether its
doorbell is enabled.
Create two new device models ivshmem-plain and ivshmem-doorbell, and
deprecate the old one.
Changes from ivshmem:
* PCI revision is 1 instead of 0. The new revision is fully backwards
compatible for guests. Guests may elect to require at least
revision 1 to make sure they're not exposed to the funny "no shared
memory, yet" state.
* Property "role" replaced by "master". role=master becomes
master=on, role=peer becomes master=off. Default is off instead of
auto.
* Property "use64" is gone. The new devices always have 64 bit BARs.
Changes from ivshmem to ivshmem-plain:
* The Interrupt Pin register in PCI config space is zero (does not use
an interrupt pin) instead of one (uses INTA).
* Property "x-memdev" is renamed to "memdev".
* Properties "shm" and "size" are gone. Use property "memdev"
instead.
* Property "msi" is gone. The new device can't have MSI-X capability.
It can't interrupt anyway.
* Properties "ioeventfd" and "vectors" are gone. They're meaningless
without interrupts anyway.
Changes from ivshmem to ivshmem-doorbell:
* Property "msi" is gone. The new device always has MSI-X capability.
* Property "ioeventfd" defaults to on instead of off.
* Property "size" is gone. The new device can only map all the shared
memory received from the server.
Guests can easily find out whether the device is configured for
interrupts by checking for MSI-X capability.
Note: some code added in sub-optimal places to make the diff easier to
review. The next commit will move it to more sensible places.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-37-git-send-email-armbru@redhat.com>
This kills off the funny state described in the previous commit.
Simplify ivshmem_io_read() accordingly, and update documentation.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1458066895-20632-27-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Option parameter "share" is missing. Without it, you get a *private*
mmap(), which defeats ivshmem's purpose pretty thoroughly ;)
While there, switch to the conventional mountpoint of hugetlbfs
/dev/hugepages.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1458066895-20632-5-git-send-email-armbru@redhat.com>
The current documentation of chardev mux=on is rather brief and opaque;
expand it to hopefully be a bit more helpful.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1455643738-6068-1-git-send-email-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Libtool support was needed to build shared library for libcacard.
Now there's no need to use libtool, and since the build system is
already complicated enough, we have a way to slightly de-complicate
it.
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Since -smb and -redir are deprecated options, we should not
use them as examples in the documentation anymore.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Add the basic IPMI types and infrastructure to QEMU. Low-level
interfaces and simulation interfaces will register with this; it's
kind of the go-between to tie them together.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The device's guest interface and its QEMU user interface are
flawed^Whotly debated. We'll resolve that in the next development
cycle, probably by deprecating the device in favour of a cleaned up,
but not quite compatible revision.
To avoid adding more baggage to the soon-to-be-deprecated interface,
mark property "memdev" as experimental, by renaming it to "x-memdev".
It's the only recent user interface change.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1448384789-14830-6-git-send-email-armbru@redhat.com>
[Update of qemu-doc.texi squashed in]
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
The example suggests you can omit "shm". This isn't true; you must
specify exactly one of "shm", "chardev", "memdev". Fix it.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1448384789-14830-3-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Use @var{foo} like we do everywhere else, not <foo>.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1448384789-14830-2-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
This allows to explicitly specify file name to use with the backend. This
is important when using it together with ivshmem in order to make it backed
by hugetlbfs. By default filename is autogenerated using mkstemp(), and the
file is unlink()ed after creation, effectively making it anonymous. This is
not very useful with ivshmem because it ends up in a memory which cannot be
accessed by something else.
Distinction between directory and file name is done by stat() check. If an
existing directory is given, the code keeps old behavior. Otherwise it
creates or opens a file with the given pathname.
Signed-off-by: Pavel Fedin <p.fedin@samsung.com>
Tested-by: Igor Skalkin <i.skalkin@samsung.com>
Message-Id: <004301d11166$9672fe30$c358fa90$@samsung.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Document and give some examples of hugepages support with ivshmem device
and server.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
When using ivshmem devices, notifications between guests can be sent as
interrupts using a ivshmem-server (typical use described in documentation).
The client is provided as a debug tool.
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: David Marchand <david.marchand@6wind.com>
[fix a valgrind warning, option and server_close() segvs, extra server
headers includes, getopt() return type, out-of-tree build, use qemu
event_notifier instead of eventfd, fix x86/osx warnings - Marc-André]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
It will be easier if you need to add info-commands to edit
only hmp-commands-info.hx, before this had to edit monitor.c and
hmp-commands.hx.
From the build point of view all documentation is saved into
qemu-monitor-info.texi which from now on is used for all user
documentation building.
Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1441899541-1856-5-git-send-email-den@openvz.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Many source files have doubled words (eg "the the", "to to",
and so on). Most of these can simply be removed, but a couple
were actual mis-spellings (eg "to to" instead of "to do").
There was even one triple word score "to to to" :-)
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Add a simple man page for the qemu agent.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*squashed in review comments from Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Fix a capitalization error in the OS X build instructions;
this was picked up in review of commit b352153f5f and intended to be
corrected before I applied it, but I accidentally didn't include it.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
qemu-doc.texi: Add information on compiling source code on Mac OS X
Add information to the documentation on how to build QEMU
on Mac OS X.
Signed-off-by: John Arbuckle <programmingkidx@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: fixed a minor capitalization error]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Raise your hand if you have a physical floppy drive in a computer
you've powered on in 2015. Okay, I see we got a few weirdos in the
audience. That's okay, weirdos are welcome here.
Kidding aside, media change detection doesn't fully work, isn't going
to be fixed, and floppy passthrough just isn't earning its keep
anymore.
Deprecate block driver host_floppy now, so we can drop it after a
grace period.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We've steered users away from QCOW/QCOW2 encryption for a while,
because it's a flawed design (commit 136cd19 Describe flaws in
qcow/qcow2 encryption in the docs).
In addition to flawed crypto, we have comically bad usability, and
plain old bugs. Let me show you.
= Example images =
I'm going to use a raw image as backing file, and two QCOW2 images,
one encrypted, and one not:
$ qemu-img create -f raw backing.img 4m
Formatting 'backing.img', fmt=raw size=4194304
$ qemu-img create -f qcow2 -o encryption,backing_file=backing.img,backing_fmt=raw geheim.qcow2 4m
Formatting 'geheim.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=on cluster_size=65536 lazy_refcounts=off
$ qemu-img create -f qcow2 -o backing_file=backing.img,backing_fmt=raw normal.qcow2 4m
Formatting 'normal.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=off cluster_size=65536 lazy_refcounts=off
= Usability issues =
== Confusing startup ==
When no image is encrypted, and you don't give -S, QEMU starts the
guest immediately:
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio normal.qcow2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) info status
VM status: running
But as soon as there's an encrypted image in play, the guest is *not*
started, with no notification whatsoever:
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) info status
VM status: paused (prelaunch)
If the user figured out that he needs to type "cont" to enter his
keys, the confusion enters the next level: "cont" asks for at most
*one* key. If more are needed, it then silently does nothing. The
user has to type "cont" once per encrypted image:
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio -drive if=none,file=geheim.qcow2 -drive if=none,file=geheim.qcow2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) info status
VM status: paused (prelaunch)
(qemu) c
none0 (geheim.qcow2) is encrypted.
Password: ******
(qemu) info status
VM status: paused (prelaunch)
(qemu) c
none1 (geheim.qcow2) is encrypted.
Password: ******
(qemu) info status
VM status: running
== Incorrect passwords not caught ==
All existing encryption schemes give you the GIGO treatment: garbage
password in, garbage data out. Guests usually refuse to mount
garbage, but other usage is prone to data loss.
== Need to stop the guest to add an encrypted image ==
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) info status
VM status: running
(qemu) drive_add "" if=none,file=geheim.qcow2
Guest must be stopped for opening of encrypted image
(qemu) stop
(qemu) drive_add "" if=none,file=geheim.qcow2
OK
Commit c3adb58 added this restriction. Before, we could expose images
lacking an encryption key to guests, with potentially catastrophic
results. See also "Use without key is not always caught".
= Bugs =
== Use without key is not always caught ==
Encrypted images can be in an intermediate state "opened, but no key".
The weird startup behavior and the need to stop the guest are there to
ensure the guest isn't exposed to that state. But other things still
are!
* drive_backup
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) drive_backup -f ide0-hd0 out.img raw
Formatting 'out.img', fmt=raw size=4194304
I guess this writes encrypted data to raw image out.img. Good luck
with figuring out how to decrypt that again.
* commit
$ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) commit ide0-hd0
I guess this writes encrypted data into the unencrypted raw backing
image, effectively destroying it.
== QMP device_add of usb-storage fails when it shouldn't ==
When the image is encrypted, device_add creates the device, defers
actually attaching it to when the key becomes available, then fails.
This is wrong. device_add must either create the device and succeed,
or do nothing and fail.
$ qemu-system-x86_64 -nodefaults -display none -usb -qmp stdio -drive if=none,id=foo,file=geheim.qcow2
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 2}, "package": ""}, "capabilities": []}}
{ "execute": "qmp_capabilities" }
{"return": {}}
{ "execute": "device_add", "arguments": { "driver": "usb-storage", "id": "bar", "drive": "foo" } }
{"error": {"class": "DeviceEncrypted", "desc": "'foo' (geheim.qcow2) is encrypted"}}
{"execute":"device_del","arguments": { "id": "bar" } }
{"timestamp": {"seconds": 1426003440, "microseconds": 237181}, "event": "DEVICE_DELETED", "data": {"path": "/machine/peripheral/bar/bar.0/legacy[0]"}}
{"timestamp": {"seconds": 1426003440, "microseconds": 238231}, "event": "DEVICE_DELETED", "data": {"device": "bar", "path": "/machine/peripheral/bar"}}
{"return": {}}
This stuff is worse than useless, it's a trap for users.
If people become sufficiently interested in encrypted images to
contribute a cryptographically sane implementation for QCOW2 (or
whatever other format), then rewriting the necessary support around it
from scratch will likely be easier and yield better results than
fixing up the existing mess.
Let's deprecate the mess now, drop it after a grace period, and move
on.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The VHDX spec specifies that the default new block state is
PAYLOAD_BLOCK_NOT_PRESENT for a dynamic VHDX image, and
PAYLOAD_BLOCK_FULLY_PRESENT for a fixed VHDX image.
However, in order to create space-efficient VHDX images with qemu-img
convert, it is desirable to be able to set has_zero_init to true for
VHDX.
There is currently an option when creating VHDX images, to use block
state ZERO for new blocks. However, this currently defaults to 'off'.
In order to be able to eventually set has_zero_init to true for VHDX,
this needs to default to 'on'.
This patch changes the default to 'on', and provides some help
information to warn against setting it to 'off' when using qemu-img
convert.
[Max Reitz pointed out that a full stop was missing at the end of the
VHDX_BLOCK_OPT_ZERO option help text. I have added it.
--Stefan]
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 85164899eacc86e150c3ceba793cf93b398dedd7.1418018421.git.jcody@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch removes support for the cow file format.
Normally we do not break backwards compatibility but in this case there
is no impact and it is the most logical option. Extraordinary claims
require extraordinary evidence so I will show why removing the cow block
driver is the right thing to do.
The cow file format is the disk image format for Usermode Linux, a way
of running a Linux system in userspace. The performance of UML was
never great and it was hacky, but it enjoyed some popularity before
hardware virtualization support became mainstream.
QEMU's block/cow.c is supposed to read this image file format.
Unfortunately the file format was underspecified:
1. Earlier Linux versions used the MAXPATHLEN constant for the backing
filename field. The value of MAXPATHLEN can change, so Linux
switched to a 4096 literal but QEMU has a 1024 literal.
2. Padding was not used on the header struct (both in the Linux kernel
and in QEMU) so the struct layout varied across architectures. In
particular, i386 and x86_64 were different due to int64_t alignment
differences. Linux now uses __attribute__((packed)), QEMU does not.
Therefore:
1. QEMU cow images do not conform to the Linux cow image file format.
2. cow images cannot be shared between different host architectures.
This means QEMU cow images are useless and QEMU has not had bug reports
from users actually hitting these issues.
Let's get rid of this thing, it serves no purpose and no one will be
affected.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1410877464-20481-1-git-send-email-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
preallocation=falloc allocates disk space by posix_fallocate(),
preallocation=full allocates disk space by writing zeros to disk.
Both modes imply preallocation=metadata.
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
