linux-kernel - [PATCH 0/4] KVM: x86: Require EFER.NX support unless EPT is on

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Message-Id: <20210615164535.2146172-1-seanjc@google.com>
Date:   Tue, 15 Jun 2021 09:45:31 -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
Subject: [PATCH 0/4] KVM: x86: Require EFER.NX support unless EPT is on

KVM has silently required EFER.NX support for shadow paging for well over
a year, and for NPT for roughly the same amount of time.  Attempting to
run any VM with shadow paging on a system without NX support will fail due
to invalid state, while enabling nx_huge_pages with NPT and no NX will
explode due to setting a reserved bit in the page tables.

I really, really wanted to require NX across the board, because the lack
of bug reports for the shadow paging change strongly suggests no one is
running KVM on a CPU that truly doesn't have NX.  But, Intel CPUs let
firmware disable NX via MISC_ENABLES, so it's plausible that there are
users running KVM with EPT and no NX.

Sean Christopherson (4):
  KVM: VMX: Refuse to load kvm_intel if EPT and NX are disabled
  KVM: SVM: Refuse to load kvm_amd if NX support is not available
  KVM: x86: WARN and reject loading KVM if NX is supported but not
    enabled
  KVM: x86: Simplify logic to handle lack of host NX support

 arch/x86/kvm/cpuid.c   | 13 +++++--------
 arch/x86/kvm/svm/svm.c | 13 ++++++++++---
 arch/x86/kvm/vmx/vmx.c |  6 ++++++
 arch/x86/kvm/x86.c     |  3 +++
 4 files changed, 24 insertions(+), 11 deletions(-)

-- 
2.32.0.272.g935e593368-goog