linux-kernel - [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest

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Date:   Mon,  8 Jan 2018 19:08:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     jmattson@...gle.com, aliguori@...zon.com, thomas.lendacky@....com,
        dwmw@...zon.co.uk, bp@...en8.de
Subject: [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest

This series allows guests to use the MSR_IA32_SPEC_CTRL and
MSR_IA32_PRED_CMD model specific registers that were added as mitigations
for CVE-2017-5715.

These are only the KVM specific parts of the fix.  It does *not* yet
include any protection for reading host memory from the guest, because
that would be done in the same way as the rest of Linux.  So there is no
IBRS *usage* here, no retpolines, no stuffing of the return stack buffer.
(KVM already includes a fix to clear all registers on vmexit, which is
enough to block Google Project Zero's PoC exploit).

However, I am including the changes to use IBPB (indirect branch
predictor barrier) if available.  That occurs only when there is a VCPU
switch on a physical CPU, thus it has a small impact on performance.

The patches are a bit hackish because the relevant cpufeatures have
not been included yet, and because I wanted to make the patches easier
to backport to distro kernels if desired, but I would still like to
have them in 4.16.

Please review.

Thanks,

Paolo

Paolo Bonzini (5):
  KVM: x86: add SPEC_CTRL and IBPB_SUPPORT accessors
  x86/msr: add definitions for indirect branch predictor MSRs
  kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest
  kvm: svm: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to guest
  KVM: x86: add SPEC_CTRL and IBPB_SUPPORT to MSR and CPUID lists

Tim Chen (1):
  kvm: vmx: Set IBPB when running a different VCPU

Tom Lendacky (1):
  x86/svm: Set IBPB when running a different VCPU

 arch/x86/include/asm/msr-index.h |  5 ++++
 arch/x86/kvm/cpuid.c             | 27 +++++++++++++----
 arch/x86/kvm/cpuid.h             | 22 ++++++++++++++
 arch/x86/kvm/svm.c               | 65 +++++++++++++++++++++++++++++++++++++++-
 arch/x86/kvm/vmx.c               | 41 +++++++++++++++++++++++++
 arch/x86/kvm/x86.c               |  1 +
 6 files changed, 154 insertions(+), 7 deletions(-)

-- 
1.8.3.1