linux-kernel - Re: [PATCH] KVM: SVM: fix task switch emulation on INTn instruction.

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Date:   Thu, 14 Jul 2022 15:50:37 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: SVM: fix task switch emulation on INTn instruction.

On 14.07.2022 14:44, Maxim Levitsky wrote:
> Recently KVM's SVM code switched to re-injecting software interrupt events,
> if something prevented their delivery.
> 
> Task switch due to task gate in the IDT, however is an exception
> to this rule, because in this case, INTn instruction causes
> a task switch intercept and its emulation completes the INTn
> emulation as well.
> 
> Add a missing case to task_switch_interception for that.
> 
> This fixes 32 bit kvm unit test taskswitch2.
> 
> Fixes: 7e5b5ef8dca322 ("KVM: SVM: Re-inject INTn instead of retrying the insn on "failure"")
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---

That's a good catch, your patch looks totally sensible to me.
People running Win 3.x or OS/2 on top of KVM will surely be grateful for it :)

Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>

Thanks,
Maciej