linux-kernel - Re: [PATCH v2 02/11] KVM: SVM: Don't BUG if userspace injects a soft interrupt with GIF=0

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Message-ID: <b8a02f2eab780262c172cd4bbffd801ca8a37e98.camel@redhat.com>
Date:   Thu, 28 Apr 2022 17:34:44 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 02/11] KVM: SVM: Don't BUG if userspace injects a
 soft interrupt with GIF=0

On Thu, 2022-04-28 at 15:27 +0200, Maciej S. Szmigiero wrote:
> On 28.04.2022 09:35, Maxim Levitsky wrote:
> > On Sat, 2022-04-23 at 02:14 +0000, Sean Christopherson wrote:
> > > From: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
> > > 
> > > Don't BUG/WARN on interrupt injection due to GIF being cleared if the
> > > injected event is a soft interrupt, which are not actually IRQs and thus
> > 
> > Are any injected events subject to GIF set? I think that EVENTINJ just injects
> > unconditionaly whatever hypervisor puts in it.
> 
> That's right, EVENTINJ will pretty much always inject, even when the CPU
> is in a 'wrong' state (like for example, injecting a hardware interrupt
> or a NMI with GIF masked).
> 
> But KVM as a L0 is not supposed to inject a hardware interrupt into guest
> with GIF unset since the guest is obviously not expecting it then.
> Hence this WARN_ON().

If you mean L0->L1 injection, that sure, but if L1 injects interrupt to L2,
then it should always be allowed to do so.


I am not sure that I am right here, just noticed something odd. I'll take
a better look at this next week.


Best regards,
	Maxim levitsky

> 
> > Best regards,
> > 	Maxim Levitsky
> 
> Thanks,
> Maciej
>