amd64/175780: Crash on KVM boot due to xsave instruction issue

[Kaloyan Ganchev]

>Number:         175780
>Category:       amd64
>Synopsis:       Crash on KVM boot due to xsave instruction issue
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Feb 02 13:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Kaloyan Ganchev
>Release:        9.1
>Organization:
>Environment:
>Description:
When trying to boot FreeBSD 9.1 on kvm host  with the following command:

kvm -cpu core2duo,+xsave -enable-kvm -drive file=freebsd-9.1-qcow2.img -boot d -net nic -net user -nographic -vnc :0  -cdrom ./isos/FreeBSD-9.1-RELEASE-amd64-disc1.iso 

The kernel return the following error immediately after taking over from the loader:

panic: CPU0 does not support X87 or SSE : 0

If I do not expose the xsave cpu flag to the FreeBSD guest the virtual machine boot as expected.
This problem do not appear in 9.1 i386 and 9.0 amd64 releases.
Also I tried several other cpu models instead of the core2duo and it doesn't make a difference, if xsave is exposed to the guest, FreeBSD 9.1 amd64 fails to boot with the error above.
>How-To-Repeat:
kvm -cpu core2duo,+xsave -enable-kvm -drive file=freebsd-9.1-qcow2.img -boot d -net nic -net user -nographic -vnc :0  -cdrom ./isos/FreeBSD-9.1-RELEASE-amd64-disc1.iso 
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: