linux-kernel - Re: [PATCH 0/2] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

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Message-ID: <ZOeAb0ccVjdw3Gvw@google.com>
Date:   Thu, 24 Aug 2023 09:08:15 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Wu Zongyo <wuzongyo@...l.ustc.edu.cn>
Subject: Re: [PATCH 0/2] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

On Wed, Aug 23, 2023, Sean Christopherson wrote:
> One idea to make the original bug repro on every run would be to constantly
> toggle nx_huge_pages between "off" and "force" while the guest is booting.  Toggling
> nx_huge_pages should force KVM to rebuild the SPTEs and all but guarantee trying
> to deliver the #BP will hit a #NPF.

Mwhahaha.  That, plus a delay in the guest and disabling THP, makes this 100%
reproducible.  I'll verify the fix actually works before posting v2.