linux-kernel - [PATCH 0/4] KVM: x86/mmu: Bug fixes and cleanups in get_mmio

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Message-ID: <2001245.9o76ZdvQCi@starbug.dom>
Date:   Thu, 17 Dec 2020 20:27:38 -0500
From:   Richard Herbert <rherbert@...patico.ca>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 0/4] KVM: x86/mmu: Bug fixes and cleanups in get_mmio_spte()

 Hi, Sean and all.

Thanks so much for these.  Very glad to report that the problem has been 
solved.  I applied all four patches, recompiled kernel 5.10.1 and successfully 
launched a Qemu VM.  Let's hope these will get merged into 5.10.2.

Thanks again for the hard work and quick fix.

Richard Herbert


On Thursday, December 17, 2020 7:31:35 PM EST Sean Christopherson wrote:

> Two fixes for bugs that were introduced along with the TDP MMU (though I
> strongly suspect only the one reported by Richard, fixed in patch 2/4, is
> hittable in practice).  Two additional cleanup on top to try and make the
> code a bit more readable and shave a few cycles.
> 
> Sean Christopherson (4):
>   KVM: x86/mmu: Use -1 to flag an undefined spte in get_mmio_spte()
>   KVM: x86/mmu: Get root level from walkers when retrieving MMIO SPTE
>   KVM: x86/mmu: Use raw level to index into MMIO walks' sptes array
>   KVM: x86/mmu: Optimize not-present/MMIO SPTE check in get_mmio_spte()
> 
>  arch/x86/kvm/mmu/mmu.c     | 53 +++++++++++++++++++++-----------------
>  arch/x86/kvm/mmu/tdp_mmu.c |  9 ++++---
>  arch/x86/kvm/mmu/tdp_mmu.h |  4 ++-
>  3 files changed, 39 insertions(+), 27 deletions(-)