linux-kernel - Re: [PATCH 00/24] KVM: nSVM: event fixes and migration support

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Message-ID: <2401913621cc7686d71f491ef55f30f78ebbb2eb.camel@redhat.com>
Date:   Thu, 21 May 2020 00:08:42 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     vkuznets@...hat.com, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 00/24] KVM: nSVM: event fixes and migration support

On Wed, 2020-05-20 at 22:42 +0200, Paolo Bonzini wrote:
> On 20/05/20 21:24, Maxim Levitsky wrote:
> > Patch 24 doesn't apply cleanly on top of kvm/queue, I appplied it manually,
> > due to missing KVM_STATE_NESTED_MTF_PENDING bit
> > 
> > Also patch 22 needes ALIGN_UP which is not on mainline.
> > Probably in linux-next?
> 
> Just replace it with ALIGN.  (I tested it with memzero_user in
> arch/x86/kvm/ for convenience, and the lib/ patch ended up out of sync
> with the actual code).
That is exactly what I did.

> 
> > With these fixes, I don't see #DE exceptions on a nested guest I try to run
> > however it still hangs, right around the time it tries to access PS/2 keyboard/mouse.
> 
> IIRC you said that the bug appeared with the vintr rework, and then went
> from hang to #DE and now back to hang?  And the hang is reported by L2,
> not L1?
Yes, and now the hang appears to be deterministic. The initial hang could happen
randomally. I remember that once the nested guest got to getty prompt even and hanged
on shutdown. Now hang is deterministic when kernel prints something about PS/2.
I will re-check this tomorrow.

> 
> In order to debug the hang, a good start would be to understand if it
> also happens with vgif=0.  This is because with vgif=1 we use VINTR
> intercepts even while GIF=0, so the whole thing is a bit more complicated.
I will check this tomorrow as well.


Best regards,
	Maxim Levitsky

> 
> Paolo
>