Bug 812295

Have changed -m 2G to -m 2048 - helped.
After conversion:
---------------------------------------------------------------------------
<domain type='qemu' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>unnamed</name>
  <uuid>8eb76e3e-52fc-6469-4725-31653c3f4c60</uuid>
  <memory>2097152</memory>
  <currentMemory>2097152</currentMemory>
  <vcpu>4</vcpu>
  <os>
    <type arch='x86_64'>hvm</type>
  </os>
  <features>
    <acpi/>
  </features>
  <cpu match='exact'>
    <model>qemu64</model>
  </cpu>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>destroy</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/local/bin/qemu-system-x86_64</emulator>
    <input type='mouse' bus='ps2'/>
    <graphics type='sdl'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
    </video>
    <memballoon model='virtio'/>
  </devices>
  <qemu:commandline>
    <qemu:arg value='-enable-kvm'/>
    <qemu:arg value='\
	-net'/>
    <qemu:arg value='nic,vlan=0,model=virtio'/>
    <qemu:arg value='\
	-net'/>
    <qemu:arg value='tap,vlan=0,ifname=tap745,script=/etc/qemu-ifup,downscript=no'/>
    <qemu:arg value='\
	-drive'/>
    <qemu:arg value='file=./rootfs_fedora_cd.img,media=cdrom'/>
    <qemu:arg value='\
	-drive'/>
    <qemu:arg value='file=./pilvi_step1.img,media=cdrom'/>
    <qemu:arg value='\
	-nographic'/>
    <qemu:arg value='\
	-kernel'/>
    <qemu:arg value='./bzImage-2.6.38.fc15.r49745'/>
    <qemu:arg value='\
	-append'/>
    <qemu:arg value='root=/dev/sr0 ro ip=192.168.44.105:192.168.44.101:192.168.44.101:255.255.255.0:pilvi-vm:eth0:off mounts=192.168.44.101:/home/khd734/test/exports/var,/var,nfs,nolock,rw console=ttyS0 earlyprintk=ttyS0 selinux=0'/>
    <qemu:arg value='\
	-name'/>
    <qemu:arg value='pilvi-vm'/>
  </qemu:commandline>
</domain>
-----------------------------------------------------------------------------

Have not found :  xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0

Have tried to bring up VM with this xml config and got:

libvir: QEMU error : internal error guest CPU is not compatible with host CPU

But again original native startup string successfuly bringing up VM.

After removing all backslashes "\" from original native string: have got an error during domxml-from-native conversion: 
error: internal error missing index/unit/bus parameter in drive 'file=./rootfs_fedora_cd.img, media=cdrom'

The index/unit/bus stuff is tracked in bug 1205925

We can use this just to track the memory 2G issue

A super simple reproducer from libvirt.git:

$ cat cmd.sh
qemu-kvm -m 2G
$ sudo ./tools/virsh domxml-from-native qemu-argv cmd.sh
error: internal error: cannot parse memory level '2G'

The error comes from src/qemu/qemu_parse_command.c qemuParseCommandLine function. The parsing only expects a straight number, not any characters. However libvirt already has a function to help parse numbers like that:

/* Scale an integer VALUE in-place by an optional case-insensitive
 * SUFFIX, defaulting to SCALE if suffix is NULL or empty (scale is
 * typically 1 or 1024).  Recognized suffixes include 'b' or 'bytes',
 * as well as power-of-two scaling via binary abbreviations ('KiB',
 * 'MiB', ...) or their one-letter counterpart ('k', 'M', ...), and
 * power-of-ten scaling via SI abbreviations ('KB', 'MB', ...).
 * Ensure that the result does not exceed LIMIT.  Return 0 on success,
 * -1 with error message raised on failure.  */
int
virScaleInteger(unsigned long long *value, const char *suffix,
                unsigned long long scale, unsigned long long limit)

See tools/vsh.c vshCommandOptScaledInt function for an easy example of how to invoke that function. Then it just needs to be adapted for the qemu code. Also 
you'll want to add a tests/qemuargv2xmltest.c test case

Fixed upstream now:

commit 701b0f1867055bce3b29d27d23c6935ce94086af
Author: Nishith Shah <nishithshah.2211>
Date:   Fri May 20 07:09:03 2016 +0000

    qemu: parse: Handle suffixes for -m memory
    
    According to QEMU docs, the '-m' option for specifying RAM is by default
    in MiB, and a suffix of "M" or "G" may be passed for values in MiB and
    GiB respectively. This commit adds support and a test for the same.
    
    Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=812295
    
    Signed-off-by: Nishith Shah <nishithshah.2211>