This reverts commit 5ac846e42e.
After further discussions with Alon Levy, I learned the following:
The use of '-vga qxl' vs. '-device qxl-vga' is completely orthogonal
to whether ram_size can be exposed. Downstream distros are interested
in backporting support for multi-head qxl, but this can be done in
one of two ways:
1. Support one head per PCI device. If you do this, then it makes
sense to have full control over the PCI address of each device. For
full control, you need '-device qxl-vga' instead of '-vga qxl'.
2. Support multiple heads through a single PCI device. If you do
this, then you need to allocate more RAM to that PCI device (enough
ram to cover the multiple screens). Here, the device is hard-coded
to 0:0:2.0, both in qemu and libvirt code.
Apparently, backporting ram_size changes to allow multiple heads in
a single device is much easier than backporting multiple device
support. Furthermore, the presence or absence of qxl-vga.surfaces
is no different than the presence or absence of qxl-vga.ram_size;
both properties can be applied regardless of whether you have one
PCI device (-vga qxl) or multiple (-device qxl-vga), so this property
is NOT a good witness of whether '-device qxl-vga' support has been
backported.
Downstream RHEL will NOT be using this patch; and worse, leaving this
patch in risks doing the wrong thing if compiling upstream libvirt
on RHEL, so the best course of action is to revert it. That means
that libvirt will go back to only using '-device qxl-vga' for qemu
>= 1.2, but this is just fine because we know of no distros that plan
on backporting multiple PCI address support to any older version of
qemu. Meanwhile, downstream can still use ram_size to pack multiple
heads through a single PCI device.
Multi-head QXL support is so useful that distros have started to
backport it to qemu earlier than 1.2. After discussion with
Alon Levy, we determined that the existence of the qxl-vga.surfaces
property is a reliable indicator of whether '-device qxl-vga' works,
or whether we have to stick to the older '-vga qxl'. I'm leaving
in the existing check for QEMU_CAPS_DEVICE_VIDEO_PRIMARY tied to
qemu 1.2 and newer (in case qemu is built without qxl support),
but for those distros that backport qxl, this additional capability
check will allow the correct command line for both RHEL 6.3 (which
lacks the feature) and RHEL 6.4 (where qemu still claims to be
version 0.12.2.x, but has backported multi-head qxl).
* src/qemu/qemu_capabilities.c (virQEMUCapsObjectPropsQxlVga): New
property test.
(virQEMUCapsExtractDeviceStr): Probe for backport of new
capability to qemu earlier than 1.2.
* tests/qemuhelpdata/qemu-kvm-1.2.0-device: Update test.
* tests/qemuhelpdata/qemu-1.2.0-device: Likewise.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel62-beta-device:
Likewise.
I was convicted that space at EOL should no be there
even for qemu help data. Hence, I've removed one in
commit bb2f621611. However, it turns out we want
it exactly the way qemu produces it. So I should undo
my premature fix. A patch against qemu has been posted
as well.
Both generated with
qemu-system-x86_64 --help > qemu-1.2.0
qemu-system-x86_64 \
-device ? \
-device pci-assign,? \
-device virtio-blk-pci,? \
-device virtio-net-pci,? \
-device scsi-disk,? \
-device PIIX4_PM,? \
-device usb-redir,? \
-device ide-drive,? \
-device usb-host,? 2> qemu-1.2.0-device
It seems I missed a few -device flags when doing this last time and I
mixed up qemu and qemu-kvm.
QEMU 1.1.0 has been officially released. With 1.1.0 QEMU went back to
three-digits version even for the initial release and I renamed the data
files to match this fact. They were generated with
qemu-system-x86_64 -help >tests/qemuhelpdata/qemu-1.1.0
qemu-system-x86_64 \
-device ? \
-device pci-assign,? \
-device virtio-blk-pci,? \
-device virtio-net-pci,? \
-device scsi-disk,? 2>tests/qemuhelpdata/qemu-1.1.0-device
Thanks to this new option we are now able to use modern CPU models (such
as Westmere) defined in external configuration file.
The qemu-1.1{,-device} data files for qemuhelptest are filled in with
qemu-1.1-rc2 output for now. I will update those files with real
qemu-1.1 output once it is released.
Now that RHEL 6.2 Beta is out, it would be nice to test multifunction
devices on that platform. This changes things so that the multifunction
cap bit can be set in two different ways: by version comparison (needed
for qemu 0.13 which lacked a -device query), and by -device query
(provided by qemu.git and backported to the RHEL beta build of
qemu-kvm which still claims to be a modified 0.12, and therefore needed
for RHEL).
* src/qemu/qemu_capabilities.c (qemuCapsParseDeviceStr): Allow
second method of setting multifunction cap bit.
* tests/qemuhelptest.c (mymain): Test it.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel62-beta: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel62-beta-device: Likewise.
This is in response to:
https://bugzilla.redhat.com/show_bug.cgi?id=629662
Explanation
qemu's virtio-net-pci driver allows setting the algorithm used for tx
packets to either "bh" or "timer". This is done by adding ",tx=bh" or
",tx=timer" to the "-device virtio-net-pci" commandline option.
'bh' stands for 'bottom half'; when this is set, packet tx is all done
in an iothread in the bottom half of the driver. (In libvirt, this
option is called the more descriptive "iothread".)
'timer' means that tx work is done in qemu, and if there is more tx
data than can be sent at the present time, a timer is set before qemu
moves on to do other things; when the timer fires, another attempt is
made to send more data. (libvirt retains the name "timer" for this
option.)
The resulting difference, according to the qemu developer who added
the option is:
bh makes tx more asynchronous and reduces latency, but potentially
causes more processor bandwidth contention since the cpu doing the
tx isn't necessarily the cpu where the guest generated the
packets.
Solution
This patch provides a libvirt domain xml knob to change the option on
the qemu commandline, by adding a new attribute "txmode" to the
<driver> element that can be placed inside any <interface> element in
a domain definition. It's use would be something like this:
<interface ...>
...
<model type='virtio'/>
<driver txmode='iothread'/>
...
</interface>
I chose to put this setting as an attribute to <driver> rather than as
a sub-element to <tune> because it is specific to the virtio-net
driver, not something that is generally usable by all network drivers.
(note that this is the same placement as the "driver name=..."
attribute used to choose kernel vs. userland backend for the
virtio-net driver.)
Actually adding the tx=xxx option to the qemu commandline is only done
if the version of qemu being used advertises it in the output of
qemu -device virtio-net-pci,?
If a particular txmode is requested in the XML, and the option isn't
listed in that help output, an UNSUPPORTED_CONFIG error is logged, and
the domain fails to start.
Qemu smartcard/spicevmc support exists on branches (such as
http://cgit.freedesktop.org/~alon/qemu/commit/?h=usb_ccid.v15&id=024a37b)
but is not yet upstream. The added -help output matches a scratch build
that will be close to the RHEL 6.1 qemu-kvm.
* src/qemu/qemu_capabilities.h (QEMUD_CMD_FLAG_CCID_EMULATED)
(QEMUD_CMD_FLAG_CCID_PASSTHRU, QEMUD_CMD_FLAG_CHARDEV_SPICEVMC):
New flags.
* src/qemu/qemu_capabilities.c (qemuCapsComputeCmdFlags)
(qemuCapsParseDeviceStr): Check for smartcard capabilities.
(qemuCapsExtractVersionInfo): Tweak comment.
* tests/qemuhelptest.c (mymain): New test.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel61: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel61-device: Likewise.
* src/qemu/qemu_capabilities.h (qemuCapsParseDeviceStr): New
prototype.
* src/qemu/qemu_capabilities.c (qemuCapsParsePCIDeviceStrs)
Rename and split...
(qemuCapsExtractDeviceStr, qemuCapsParseDeviceStr): ...to make it
easier to add and test device-specific checks.
(qemuCapsExtractVersionInfo): Update caller.
* tests/qemuhelptest.c (testHelpStrParsing): Also test parsing of
device-related flags.
(mymain): Update expected flags.
* tests/qemuhelpdata/qemu-0.12.1-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel60-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.3-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.13.0-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.13.0: New file.
* tests/qemuhelptest.c (mymain): New test from Fedora 14 qemu-kvm,
which covers some options (like -fstype passthrough) not tested elsewhere.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel60: New file.
* tests/qemuhelptest.c (mymain): New test from RHEL 6.0 qemu-kvm,
which covers some options (like -vga=qxl) not tested elsewhere.
* .x-sc_prohibit_empty_lines_at_EOF: Exempt qemu help output.
So far, readonly=on option is used when qemu supports -device. However,
there are qemu versions which support readonly option with -drive
although they don't have support for -device.
(gdb) p/x QEMUD_CMD_FLAG_VNET_HOST
$7 = 0xffffffff80000000
Oops - that meant we were incorrectly setting QEMU_CMD_FLAG_RTC_TD_HACK
for qemu-kvm-0.12.3 (and probably botching a few other settings as well).
Fixes Red Hat BZ#592070
* src/qemu/qemu_conf.h (QEMUD_CMD_FLAG_VNET_HOST): Avoid sign
extension.
* tests/qemuhelpdata/qemu-kvm-0.12.3: New file.
* tests/qemuhelptest.c (mymain): Add another case.
Probe for the new -device flag and if available set the -nodefaults
flag, instead of using -net none, -serial none or -parallel none.
Other device types will be converted to use -device in later patches.
The -nodefaults flag will help avoid unwelcome surprises from future
QEMU releases
* src/qemu/qemu_conf.c: Probe for -device. Add -nodefaults flag.
Remove -net none, -serial none or -parallel none
* src/qemu/qemu_conf.h: Define QEMU_CMD_FLAG_DEVICE
* tests/qemuhelpdata/qemu-0.12.1: New data file for 0.12.1 QEMU
* tests/qemuhelptest.c: Test feature extraction from 0.12.1 QEMU
