linux-kernel - Re: [PATCH v2 00/13] KVM: x86: Extend Spectre-v1 mitigation

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Date:   Sat, 18 Jan 2020 21:18:56 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Marios Pomonis <pomonis@...gle.com>, rkrcmar@...hat.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nick Finco <nifi@...gle.com>, Andrew Honig <ahonig@...gle.com>
Subject: Re: [PATCH v2 00/13] KVM: x86: Extend Spectre-v1 mitigation

On 11/12/19 21:47, Marios Pomonis wrote:
> From: Nick Finco <nifi@...gle.com>
> 
> This extends the Spectre-v1 mitigation introduced in
> commit 75f139aaf896 ("KVM: x86: Add memory barrier on vmcs field lookup")
> and commit 085331dfc6bb ("x86/kvm: Update spectre-v1 mitigation") in light
> of the Spectre-v1/L1TF combination described here:
> https://xenbits.xen.org/xsa/advisory-289.html
> 
> As reported in the link, an attacker can use the cache-load part of a
> Spectre-v1 gadget to bring memory into the L1 cache, then use L1TF to
> leak the loaded memory. Note that this attack is not fully mitigated by
> core scheduling; firstly when "kvm-intel.vmentry_l1d_flush" is not set
> to "always", an attacker could use L1TF on the same thread that loaded the
> memory values in the cache on paths that do not flush the L1 cache on
> VMEntry. Otherwise, an attacker could perform this attack using a
> collusion of two sibling hyperthreads: one that loads memory values in
> the cache during VMExit handling and another that performs L1TF to leak
> them.
> 
> This patch uses array_index_nospec() to prevent index computations from
> causing speculative loads into the L1 cache. These cases involve a
> bounds check followed by a memory read using the index; this is more
> common than the full Spectre-v1 pattern. In some cases, the index
> computation can be eliminated entirely by small amounts of refactoring.
> 
> Marios Pomonis (13):
>   KVM: x86: Protect x86_decode_insn from Spectre-v1/L1TF attacks
>   KVM: x86: Protect kvm_hv_msr_[get|set]_crash_data() from
>     Spectre-v1/L1TF attacks
>   KVM: x86: Refactor picdev_write() to prevent Spectre-v1/L1TF attacks
>   KVM: x86: Protect ioapic_read_indirect() from Spectre-v1/L1TF attacks
>   KVM: x86: Protect ioapic_write_indirect() from Spectre-v1/L1TF attacks
>   KVM: x86: Protect kvm_lapic_reg_write() from Spectre-v1/L1TF attacks
>   KVM: x86: Protect MSR-based index computations in
>     fixed_msr_to_seg_unit()
>   KVM: x86: Protect MSR-based index computations in pmu.h
>   KVM: x86: Protect MSR-based index computations from Spectre-v1/L1TF
>     attacks in x86.c
>   KVM: x86: Protect memory accesses from Spectre-v1/L1TF attacks in
>     x86.c
>   KVM: x86: Protect exit_reason from being used in Spectre-v1/L1TF
>     attacks
>   KVM: x86: Protect DR-based index computations from Spectre-v1/L1TF
>     attacks
>   KVM: x86: Protect pmu_intel.c from Spectre-v1/L1TF attacks
> 
>  arch/x86/kvm/emulate.c       | 11 ++++--
>  arch/x86/kvm/hyperv.c        | 10 +++--
>  arch/x86/kvm/i8259.c         |  6 ++-
>  arch/x86/kvm/ioapic.c        | 15 +++++---
>  arch/x86/kvm/lapic.c         | 13 +++++--
>  arch/x86/kvm/mtrr.c          |  8 +++-
>  arch/x86/kvm/pmu.h           | 18 +++++++--
>  arch/x86/kvm/vmx/pmu_intel.c | 24 ++++++++----
>  arch/x86/kvm/vmx/vmx.c       | 71 +++++++++++++++++++++---------------
>  arch/x86/kvm/x86.c           | 18 +++++++--
>  10 files changed, 129 insertions(+), 65 deletions(-)
> 

Queued all except patch 10, thanks.

Paolo