Re: [PATCH] [2/2] KVM: Add VT-x machine check support

Andi Kleen
2009-06-04T12:54:18Z

On Thu, Jun 04, 2009 at 03:49:03PM +0300, Avi Kivity wrote:
> Andi Kleen wrote:
> >>This assumption is incorrect. This code is executed after preemption
> >>has been enabled, and we may have even slept before reaching it.
> >>
> >
> >The only thing that counts here is the context before the machine
> >check event. If there was a vmexit we know it was in guest context.
> >
> >The only requirement we have is that we're running still on the same
> >CPU. I assume that's true, otherwise the vmcb accesses wouldn't work?
> >
>
> It's not true, we're in preemptible context and may have even slept.
>
> vmcs access work because we have a preempt notifier called when we are
> scheduled in, and will execute vmclear/vmptrld as necessary. Look at
> kvm_preempt_ops in virt/kvm_main.c.

I see. So we need to move that check earlier. Do you have a preference
where it should be?

-Andi

--
ak@linux.intel.com -- Speaking for myself only.