Re: [Qemu-devel] xsave instruction not passed through correctly on AMD hardware

[Paolo Bonzini <pbonzini@redhat.com>]

Il 11/11/2013 15:30, Owen Tuz ha scritto:
> Hi all,
> 
> We've been seeing a problem lately running FreeBSD 9.1 and 9.2 (latest
> stable) which causes the guest to crash during boot when QEMU is run on
> an AMD processor with the 'xsave' flag set. 
> 
> To reproduce this behaviour:
> 
> - Boot a FreeBSD 9.1 or 9.2 guest or even installation CD on an AMD
> processor with xsave enabled. Use '-cpu host'.
> 
> - After the bootloader, the guest will crash almost immediately with the
> message 'kernel trap 12 with interrupts disabled'. This occurs before
> any disks are loaded, so it's not possible to get a memory dump from the
> guest OS for backtrace.
> 
> - Boot again with '-cpu host,-xsave'. The guest should boot successfully.

This is probably cause by the "lightweight profiling" XSAVE extension.
KVM does not support it.  Using "-cpu host" may show problems when the
CPU has features that are not supported by KVM.

It's possible though that this has been recently fixed.  Please try
branch "next" of git://git.kernel.org/pub/scm/virt/kvm/kvm.git and
report back.

Paolo