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

Avi Kivity
2009-06-04T11:48:32Z

Andi Kleen wrote:
> [Avi could you please still consider this patch for your 2.6.31 patchqueue?
> It's fairly simple, but important to handle memory errors in guests]
>

Oh yes, and it'll be needed for -stable. IIUC, right now a machine
check is trapped by the guest, so the guest is killed instead of the host?

> +/*
> + * Trigger machine check on the host. We assume all the MSRs are already set up
> + * by the CPU and that we still run on the same CPU as the MCE occurred on.
> + * We pass a fake environment to the machine check handler because we want
> + * the guest to be always treated like user space, no matter what context
> + * it used internally.
> + */
>

This assumption is incorrect. This code is executed after preemption
has been enabled, and we may have even slept before reaching it.

NMI suffers from the same issue, see vmx_complete_interrupts(). You
could handle it the same way.

> @@ -3150,6 +3171,7 @@
> [EXIT_REASON_WBINVD] = handle_wbinvd,
> [EXIT_REASON_TASK_SWITCH] = handle_task_switch,
> [EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
> + [EXIT_REASON_MACHINE_CHECK] = handle_machine_check,
> };
>
> static const int kvm_vmx_max_exit_handlers =
>

We get both an explicit EXIT_REASON and an exception?

--
error compiling committee.c: too many arguments to function