On Mon, Dec 17, 2007 at 03:42:21PM +0000, Daniel P. Berrange wrote:
> Just testing xen-unstable on some of my machines here. I've got a failure
> to boot on a Mac Mini with a i386 Core Duo cpu.
>
> If I try to boot xen-unstable changeset 16606 from cold it will immediately
> crash with this:
>
> http://people.redhat.com/berrange/xen-3.2.0-fail.jpg
>
> Sorry for lame camera pic - this being a mac mini there's no serial card,
> or even ability to add one in :-(
>
> If I boot into Xen 3.1.0 it works fine. If I warm-reboot from Xen 3.1.0
> into Xen-unstable changeset 16606 it also works fine. So it seems only the
> boot from cold is problematic.
>
> Attaching the 'xm dmesg' output from a succesfull warm-reboot into
> xen-unstable, and the CPU info.
>
> Any ideas / suggestions ?
Converting ff16420d / vmx_cpu_up+0x25d address into a line number with
eu-addr2line, it appears as if Xen is crashing & burning in the 'wrmsr'
call in the 2nd half of this conditional from arch/x86/hvm/vmx/vmcs.c:
if ( eax & IA32_FEATURE_CONTROL_MSR_LOCK )
{
if ( !(eax & (IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_OUTSIDE_SMX |
IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX)) )
{
printk("CPU%d: VMX disabled by BIOS.\n", cpu);
return 0;
}
}
else
{
eax = (IA32_FEATURE_CONTROL_MSR_LOCK |
IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_OUTSIDE_SMX |
IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX);
wrmsr(IA32_FEATURE_CONTROL_MSR, eax, 0);
}
In Xen 3.1.0 (which works for me), the 'vmx_cpu_up' method does not exist,
but the 'start_vmx' function which does more of less the same thing
writes a slightly different msr:
if ( eax & IA32_FEATURE_CONTROL_MSR_LOCK )
{
if ( (eax & IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON) == 0x0 )
{
printk("VMX disabled by Feature Control MSR.\n");
return 0;
}
}
else
{
wrmsr(IA32_FEATURE_CONTROL_MSR,
IA32_FEATURE_CONTROL_MSR_LOCK |
IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON, 0);
}
I guess this explains why Xen-unstable works if I warm re-boot from xen-3.1.0,
because the 3.1.0 hypervisor will have already enabled and lock VMX msr.
Is it possible that older CPUs / BIOS don't play nice with the extra bit
IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX
...if they don't have SMX support ?
Regards,
Dan.
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