linux-kernel - [PATCH v2 0/3] KVM: x86/mmu: Fix TLB flushing bugs in TDP MMU

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Date:   Thu, 25 Mar 2021 13:01:16 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.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 v2 0/3] KVM: x86/mmu: Fix TLB flushing bugs in TDP MMU

Two bug fixes and a clean up involving the TDP MMU, found by inspection.

Patch 1 fixes a bug where KVM yields, e.g. due to lock contention, without
performing a pending TLB flush that was required from a previous root.

Patch 2 fixes a much more egregious bug where it fails to handle TDP MMU
flushes in NX huge page recovery.

Patch 3 explicitly disallows yielding in the TDP MMU to prevent a similar
bug to patch 1 from sneaking in.

v2:
 - Collect a review. [Ben]
 - Disallowing yielding instead of feeding "flush" into the TDP MMU. [Ben]
 - Move the yielding logic to a separate patch since it's not strictly a
   bug fix and it's standalone anyways (the flush feedback loop was not).

v1:
 - https://lkml.kernel.org/r/20210319232006.3468382-1-seanjc@google.com

Sean Christopherson (3):
  KVM: x86/mmu: Ensure TLBs are flushed when yielding during GFN range
    zap
  KVM: x86/mmu: Ensure TLBs are flushed for TDP MMU during NX zapping
  KVM: x86/mmu: Don't allow TDP MMU to yield when recovering NX pages

 arch/x86/kvm/mmu/mmu.c     |  9 +++++----
 arch/x86/kvm/mmu/tdp_mmu.c | 26 ++++++++++++++------------
 arch/x86/kvm/mmu/tdp_mmu.h | 23 ++++++++++++++++++++++-
 3 files changed, 41 insertions(+), 17 deletions(-)

-- 
2.31.0.291.g576ba9dcdaf-goog