Test case:

Run a core-image-sato (or any other image) with a qemux86-64 machine.
Wrong arguments are passed to qemu related to cpu type:

/mnt/Yo/yoctoproject/build/tmp/sysroots/x86_64-linux/usr/bin/qemu-system-x86_64 -kernel /mnt/Yo/yoctoproject/build/tmp/deploy/images/qemux86-64/bzImage-qemux86-64.bin -net nic,model=virtio -net tap,vlan=0,ifname=tap0,script=no,downscript=no,vhost=on -cpu core2duo -drive file=/mnt/Yo/yoctoproject/build/tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.ext3,if=virtio -show-cursor -usb -usbdevice wacom-tablet -vga vmware -no-reboot -enable-kvm -cpu kvm64 -m 256 --append "vga=0 uvesafb.mode_option=640x480-32 root=/dev/vda rw mem=256M ip=192.168.7.2::192.168.7.1:255.255.255.0 oprofile.timer=1 "

CPU type is set twice, and the last setting is taken into consideration, defeating the right one (-cpu core2duo).

This is related to commit: 9532004b527fdf3a819b8b0e7e64833003a4b1d4 and commit b8819b02dc4ff29d678cc55887dfe6c2d109a67d.

After the guest Linux image starts, the wrong CPU is set:

root@qemux86-64:~# cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 15
model		: 6
model name	: Common KVM processor
stepping	: 1
microcode	: 0x1
cpu MHz		: 3392.066
cache size	: 4096 KB
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm constant_tsc nopl pni cx16 hypervisor
bogomips	: 6784.13
clflush size	: 64
cache_alignment	: 128
address sizes	: 40 bits physical, 48 bits virtual
power management:

Full log attached