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

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Date:   Tue, 26 Jul 2022 17:21:57 +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, Sean Christopherson wrote:
> 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.

Hrm, not seeing failures (beyond the VMX_VMCS_ENUM.MAX_INDEX failure because I'm
running an older QEMU).

I'll follow up off-list to figure out what's going on.