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

Paolo Bonzini
2020-01-18T20:19:02Z

On 11/12/19 21:47, Marios Pomonis wrote:
> From: Nick Finco <nifi@google.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