linux-kernel - Re: [PATCH 12/13] KVM: x86: Replace late check_nested

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Date:   Wed, 29 Apr 2020 18:58:45 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Oliver Upton <oupton@...gle.com>,
        Peter Shier <pshier@...gle.com>
Subject: Re: [PATCH 12/13] KVM: x86: Replace late check_nested_events() hack
 with more precise fix

On 29/04/20 18:45, Sean Christopherson wrote:
> 
> Can you just drop 9/13, "Prioritize SMI over nested IRQ/NMI" from kvm/queue?
> It's probably best to deal with this in a new series rather than trying to
> squeeze it in.

With AMD we just have IRQ/NMI/SMI, and it's important to handle SMI in
check_nested_events because you can turn SMIs into vmexit without stuff
such as dual-monitor treatment.  On the other hand there is no MTF and
we're not handling exceptions yet.  So, since SMIs should be pretty rare
anyway, I'd rather just add a comment detailing the correct order and
why we're not following it.  The minimal fix would be to move SMI above
the preemption timer, right?

Paolo