[v2,0/4] kvm: arm64: Pointer Authentication handling fixes

Message

Marc Zyngier June 10, 2020, 11:34 a.m. UTC

I recently discovered that the Pointer Authentication (PtrAuth)
handling code in KVM is busted, and has been for a while. The main
issue is that the we save the host's keys from a preemptible
context. Things will go wrong at some point.

In order to address this, the first patch move the saving of the
host's keys to vcpu_load(). It is done eagerly, which is a bore, but
is at least safe. This is definitely stable material.

The following patch is adding an optimisatioe: we handle key saving
and HCR massaging as a fixup, much like the FPSIMD code.

Subsequent patch cleans up our HYP per-CPU accessor and make it sparse
friendly, asthe last patch makes heavy use of it by killing the
per-vcpu backpointer to the physical CPU context, avoiding the first
bug altogether.

This has been very lightly tested on a model. Unless someone shouts, I
plan to send this as part of the pending set of fixes.

* From v1:
  - Dropped the misbehaving guest handling patch
  - Added the two cleanup patches to the series (previously posted separately)

Marc Zyngier (4):
  KVM: arm64: Save the host's PtrAuth keys in non-preemptible context
  KVM: arm64: Handle PtrAuth traps early
  KVM: arm64: Stop sparse from moaning at __hyp_this_cpu_ptr
  KVM: arm64: Remove host_cpu_context member from vcpu structure

 arch/arm64/include/asm/kvm_asm.h     | 13 ++++--
 arch/arm64/include/asm/kvm_emulate.h |  6 ---
 arch/arm64/include/asm/kvm_host.h    |  3 --
 arch/arm64/kvm/arm.c                 |  6 +--
 arch/arm64/kvm/handle_exit.c         | 32 ++------------
 arch/arm64/kvm/hyp/debug-sr.c        |  4 +-
 arch/arm64/kvm/hyp/switch.c          | 65 +++++++++++++++++++++++++++-
 arch/arm64/kvm/hyp/sysreg-sr.c       |  6 ++-
 arch/arm64/kvm/pmu.c                 |  8 +---
 arch/arm64/kvm/sys_regs.c            | 13 +++---
 10 files changed, 91 insertions(+), 65 deletions(-)