Re: bugreport: guest crashes on reboot in KVM 65 on AMD

[Joerg Roedel <joerg.roedel@amd.com>]

On Mon, Apr 14, 2008 at 12:43:30PM +0300, Avi Kivity wrote:
> Michal Ludvig wrote:
> >Hi all,
> >
> >in short: CentOS 5 guest (32bit) crashes when I run "reboot" in the VM with qemu message:
> >kvm_run: failed entry, reason 65535
> >kvm_run returned -8
> >
> >In dmesg is this message:
> >kvm: 23769: cpu0 kvm_set_msr_common: MSR_IA32_MC0_STATUS 0x0, nop
> >
> >Details:
> >KVM 65
> >Host is openSUSE 10.3 with my own 2.6.24, 64 bit
> >Guest is CentOS 5.1 with 2.6.18-53.1.14.el5, 32 bit
> >GCC 4.2.1 for module, GCC 3.3.3 for qemu
> >CPU "AMD Athlon(tm) 64 X2 Dual Core Processor 5600+"
> >
> >Everything works fine, except that I can't reboot the guest. In VNC it says "md: stopping devices" and then Qemu exits with:
> >kvm_run: failed entry, reason 65535
> >kvm_run returned -8
> >
> >IIRC reboot used to work with kvm-64
> >  
> 
> I think two bugs are involved:
> 
> - the guest invokes the triple-fault shutdown path, so it seems normal reboot doesn't work with iothread.  Haven't looked as to why yet.
> - amd shutdown interception clears the vmcb, leaving asid == 0, which is illegal.  Adding force_new_asid() fixes this.  There are probably 
> other issues with clearing the vmcb as well.
> 
> Joerg, can you find out if the "vmcb is undefined" applies to the entire vmcb or just the guest saved state?  Is there a way to 
> differentiate between a guest initiated shutdown due to triple fault and the core melting down?

Only the state saved in the VMCB is undefined after an intercepted
shutdown event. I am not sure if I understand your second question, what
do you mean with "core melting down" vs. guest initiated shutdown?

Joerg


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