linux-kernel - Re: [PATCH v2 0/6] KVM: x86: Apply NX mitigation more precisely

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Message-ID: <YuAZDbg9Dzw0LKkp@google.com>
Date:   Tue, 26 Jul 2022 16:40:45 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Mingwei Zhang <mizhang@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yosry Ahmed <yosryahmed@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v2 0/6] KVM: x86: Apply NX mitigation more precisely

On Tue, Jul 26, 2022, Mingwei Zhang wrote:
> On Sat, Jul 23, 2022, Sean Christopherson wrote:
> > Patch 6 from Mingwei is the end goal of the series.  KVM incorrectly
> > assumes that the NX huge page mitigation is the only scenario where KVM
> > will create a non-leaf page instead of a huge page.   Precisely track
> > (via kvm_mmu_page) if a non-huge page is being forced and use that info
> > to avoid unnecessarily forcing smaller page sizes in
> > disallowed_hugepage_adjust().
> > 
> > v2: Rebase, tweak a changelog accordingly.
> 
> hmm, I applied this patch set (v2) on top of kvm/queue (HEAD:
> 1a4d88a361af) and it seems kvm-unit-tests/vmx failed on both ept=1 and
> ept=0. And it did not work on our internel kernel either (kernel
> crashed).
> 
> Maybe there is still minor issues?

Heh, or not so minor issues.  I'll see what I broke.  I have a bad feeling that
it's the EPT tests; IIRC I only ran VMX on a platform with MAXPHYADDR < 40.