linux-kernel - Re: [PATCH 1/9] KVM: SVM: Notify nested hypervisor of lost event injections

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Date:	Mon, 12 Oct 2009 11:34:55 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Alexander Graf <agraf@...e.de>
CC:	Joerg Roedel <joerg.roedel@....com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/9] KVM: SVM: Notify nested hypervisor of lost event
 injections

On 10/08/2009 06:46 PM, Alexander Graf wrote:
>
>
> Am 08.10.2009 um 18:38 schrieb Avi Kivity <avi@...hat.com>:
>
>> On 10/08/2009 06:32 PM, Joerg Roedel wrote:
>>> No. The L1 guest needs to execute VMRUN with an interrupt to inject to
>>> the L2 guest with event_inj. On that VMRUN instruction emulation an
>>> interrupt becomes pending which causes an immediate #vmexit from L2 to
>>> L2 again without even entering the L2 guest. The bug was that in this
>>> case the event which the L1 tried to inject in the L2 was lost because
>>> it was not copied to exit_int_info.
>>>
>>
>> (from L1 to L0?)
>>
>> Wow.  Alex, how did you find this?
>
> Hyper-V got stuck and I was trying to think of possible reasons 
> looking at the logs :-).
> Fortunately this patch also seemed to make things work better with KVM 
> in KVM.
>
> Doesn't really help with regression testing though...

We could write a dummy hypervisor that injects tons of interrupts and 
hope for a host interrupt in there.  I'm worried about such a mass of 
complex code that gets very little testing.

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

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