Re: [PATCH 2/2] KVM: SVM: check for progress after IRET interception

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-02-03 16:58, Avi Kivity wrote:
> On 02/03/2011 05:55 PM, Jan Kiszka wrote:
>>>
>>>  What's an interrupt window without IRET interception?
>>
>> I don't the details, but I thought you could get something like an
>> interrupt-window-open interception by (fake-)injecting an IRQ and
>> intercepting on VIRQ acceptance. That will not work if returning to and
>> staying in irq-disabled guest code, therefore the timeout, but it should
>> be most efficient (specifically if the guest uses NMIs for things like
>> perf).
>>
> 
> Since NMIs are used to break out of irq-disabled regions (watchdog, NMI 
> IPIs during reboots) I'm wary of such a solution.

Right, but we already use it for Intel. The timeout ensures that you
can't get stuck forever. I think Xen works this way as well (minus the
timeout - last time I checked).

I hope AMD would finally realize what the left behind and improve it so
that we can declare whatever "nice" solution just a temporary
workaround. Will still take a few years, but we had the same situation
on Intel.

Jan

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