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: <4baa5071-3fb6-64f3-bcd7-2ffc1181d811@maciej.szmigiero.name>
Date:   Thu, 28 Apr 2022 15:27:01 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Maxim Levitsky <mlevitsk@...hat.com>
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 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().

> Best regards,
> 	Maxim Levitsky

Thanks,
Maciej