qemu_process: Make qemuProcessReadLog() more versatile and reusable

Teach the function to skip character device definitions printed by qemu
at startup in addition to libvirt log messages and make it usable from
outside of qemu_process.c. Also add documentation about the func.
qemu: monitor: Add infrastructure to access VM logs for better err msgs

Early VM startup errors usually produce a better error message in the
machine log file. Currently we were accessing it only when the process
exited during certain phases of startup. This will help adding a more
comprehensive error extraction for early qemu startup phases.

This patch adds infrastructure to keep a file descriptor for the machine
log file that will be used in case an error happens.
qemu: monitor: Produce better errors on monitor hangup

Change the monitor error code to add the ability to access the qemu log
file using a file descriptor so that we can dig in it for a more useful
error message. The error is now logged on monitor hangups and overwrites
a possible lesser error. A hangup on the monitor usualy means that qemu
has crashed and there's a significant chance it produced a useful error
message.

The functionality will be latent until the next patch.
qemu: Wire up better early error reporting

The previous patches added infrastructure to report better errors from
monitor in some cases. This patch finalizes this "feature" by enabling
this enhanced error reporting on early phases of VM startup. In these
phases the possibility of qemu producing a useful error message is
really high compared to running it during the whole life cycle. After
the start up is complete, the feature is disabled to provide the usual
error messages so that users are not confused by possibly irrelevant
messages that may be in the domain log.

The original motivation to do this enhancement is to capture errors when
using VFIO device passthrough, where qemu reports errors after the
monitor is initialized and the existing error catching code couldn't
catch this producing a unhelpful message:

 # virsh start test
 error: Failed to start domain test
 error: Unable to read from monitor: Connection reset by peer

With this change, the message is changed to:

 # virsh start test
 error: Failed to start domain test
 error: internal error: early end of file from monitor: possible problem:
 qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: vfio: error, group 8 is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.
 qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: vfio: failed to get group 8
 qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: Device 'vfio-pci' could not be initialized
util/viriptables: add/remove rules that short-circuit masquerading

The functions
- iptablesAddForwardDontMasquerade(),
- iptablesRemoveForwardDontMasquerade
handle exceptions in the masquerading implemented in the POSTROUTING chain
of the "nat" table. Such exceptions should be added as chronologically
latest, logically top-most rules.

The bridge driver will call these functions beginning with the next patch:
some special destination IP addresses always refer to the local
subnetwork, even though they don't match any practical subnetwork's
netmask. Packets from virbrN targeting such IP addresses are never routed
outwards, but the current rules treat them as non-virbrN-destined packets
and masquerade them. This causes problems for some receivers on virbrN.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
bridge driver: don't masquerade local subnet broadcast/multicast packets

Packets sent by guests on virbrN, *or* by dnsmasq on the same, to
- 255.255.255.255/32 (netmask-independent local network broadcast
  address), or to
- 224.0.0.0/24 (local subnetwork multicast range)
are never forwarded, hence it is not necessary to masquerade them.

In fact we must not masquerade them: translating their source addresses or
source ports (where applicable) may confuse receivers on virbrN.

One example is the DHCP client in OVMF (= UEFI firmware for virtual
machines):

  http://thread.gmane.org/gmane.comp.bios.tianocore.devel/1506/focus=2640

It expects DHCP replies to arrive from remote source port 67. Even though
dnsmasq conforms to that, the destination address (255.255.255.255) and
the source address (eg. 192.168.122.1) in the reply allow the UDP
masquerading rule to match, which rewrites the source port to or above
1024. This prevents the DHCP client in OVMF from accepting the packet.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=709418

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
qemu: eliminate redundant if clauses in qemuCollectPCIAddress

Replace them with switch cases. This will make it more efficient when
we add exceptions for more controller types, and other device types.

This is a prerequisite for patches to resolve:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983
qemu: allow some PCI devices to be attached to PCIe slots

Part of the resolution to:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983

Although most devices available in qemu area defined as PCI devices,
and strictly speaking should only be attached via a PCI slot, in
practice qemu allows them to be attached to a PCIe slot and sometimes
this makes sense.

For example, The UHCI and EHCI USB controllers are usually attached
directly to the PCIe "root complex" (i.e. PCIe slots) on real
hardware, so that should be possible for a Q35-based qemu virtual
machine as well.

We still want to prefer a standard PCI slot when auto-assigning
addresses, though, and in general to disallow attaching PCI devices
via PCIe slots.

This patch makes that possible by adding a new
QEMU_PCI_CONNECT_TYPE_EITHER_IF_CONFIG flag. Three things are done
with this flag:

1) It is set for the "pcie-root" controller

2) qemuCollectPCIAddress() now has a set of nested switches that set
this "EITHER" flag for devices that we want to allow connecting to
pcie-root when specifically requested in the config.

3) qemuDomainPCIAddressFlagsCompatible() adds this new flag to the
"flagsMatchMask" if the address being checked came from config rather
than being newly auto-allocated by libvirt (this knowledge is
conveniently already available in the "fromConfig" arg).

Now any device having the EITHER flag set can be connected to
pcie-root if explicitly requested, but auto-allocated addresses for
those devices will still be standard PCI slots instead.

This patch only loosens the restrictions on devices that have been
specifically requested, but the setup is such that it should be fairly
easy to add new devices.
qemu: replace multiple strcmps with a switch on an enum

I'm not sure why this code was written to compare the strings that it
had just retrieved from an enum->string conversion, rather than just
look at the original enum values, but this yields the same results,
and is much more efficient (especially as you add more devices).

This is a prerequisite for patches to resolve:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983
qemu: support ich9-intel-hda audio device

This resolves one of the issues in:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983

This device is identical to qemu's "intel-hda" device (known as "ich6"
in libvirt), but has a different PCI device ID (which matches the ID
of the hda audio built into the ich9 chipset, of course). It's not
supported in earlier versions of qemu, so it requires a capability
bit.
qemu: turn if into switch in qemuDomainValidateDevicePCISlotsQ35

This will make it simpler to add checks for other types of
controllers.

This is a prerequisite for patches to resolve:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983
qemu: prefer to put a Q35 machine's dmi-to-pci-bridge at 00:1E.0

This resolves one of the issues listed in:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983

00:1E.0 is the location of this controller on at least some actual Q35
hardware, so we try to replicate the placement. The bridge should work
just as well in any other location though, so if 00:1E.0 isn't
available, just allow it to be auto-assigned anywhere appropriate.
Fix leak in virDomainVcpuPinDefArrayFree

If virDomainVcpuPinDefArrayFree is called with def != NULL,
but nvcpupin == 0, then it leaks memory for 'def'. This is
an unusual scenario, but it hits when cleaning up after an
OOM during parsing of XML.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Avoid leak if virDomainSoundCodecDefParseXML return error

If virDomainSoundCodecDefParseXML returns an error (eg due
to OOM), then the xml nodeset codecNodes is leaked.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Fix leak in virDomainVcpuPinDefParseXML parsing cpumask

If the virBitmapParse method fails due to OOM, we leak
the 'tmp' variable string.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Fix leak in virDomainDefParseXML parsing vcpupin

If virBitmapNew fails due to OOM, the 'vcpupin' variable
is leaked.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Fix leak of address string in qemuDomainPCIAddressGetNextSlot

qemuDomainPCIAddressGetNextSlot has a loop for finding
compatible PCI buses. In the loop body it creates a
PCI address string, but never frees this. This causes
a leak if the loop executes more than one iteration,
or if a call in the loop body fails.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Avoid leak in qemuParseRBDString on failure of qemuAddRBDHost

If qemuAddRBDHost fails due to parsing problems or OOM, then
qemuParseRBDString cleanup is skipped causing a memory leak.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Fix failure to honour OOM status in qemuParseNBDString

In qemuParseNBDString, if the virURIParse fails, the
error is not reported to the caller. Instead execution
falls through to the non-URI codepath causing memory
leaks later on.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Fix leak on OOM in qemuBuildCommandLine dealing with sound card

The qemuBuildCommandLine code for parsing sound cards will leak
an intermediate variable if an OOM occurs. Move the free'ing of
the variable earlier to avoid the leak.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>