[0/3] KVM: arm64: support MTE in protected VMs

Message

Peter Collingbourne June 23, 2022, 2:19 a.m. UTC

Hi,

This patch series contains a proposed extension to pKVM that allows MTE
to be exposed to the protected guests. It is based on the base pKVM
series previously sent to the list [1] and later rebased to 5.19-rc2
and uploaded to [2].

This series takes precautions against host compromise of the guests
via direct access to their tag storage, by preventing the host from
accessing the tag storage via stage 2 page tables. The device tree
must describe the physical memory address of the tag storage, if any,
and the memory nodes must declare that the tag storage location is
described. Otherwise, the MTE feature is disabled in protected guests.

Now that we can easily do so, we also prevent the host from accessing
any unmapped reserved-memory regions without a driver, as the host
has no business accessing that memory.

A proposed extension to the devicetree specification is available at
[3], a patched version of QEMU that produces the required device tree
nodes is available at [4] and a patched version of the crosvm hypervisor
that enables MTE is available at [5].

[1] https://lore.kernel.org/all/[e-mail]/
[2] https://android-kvm.googlesource.com/linux/ for-upstream/pkvm-base-v2
[3] https://github.com/pcc/devicetree-specification mte-alloc
[4] https://github.com/pcc/qemu mte-shared-alloc
[5] https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3719324

Peter Collingbourne (3):
  KVM: arm64: add a hypercall for disowning pages
  KVM: arm64: disown unused reserved-memory regions
  KVM: arm64: allow MTE in protected VMs if the tag storage is known

 arch/arm64/include/asm/kvm_asm.h              |  1 +
 arch/arm64/include/asm/kvm_host.h             |  6 ++
 arch/arm64/include/asm/kvm_pkvm.h             |  4 +-
 arch/arm64/kernel/image-vars.h                |  3 +
 arch/arm64/kvm/arm.c                          | 83 ++++++++++++++++++-
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
 arch/arm64/kvm/hyp/include/nvhe/pkvm.h        |  1 +
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            |  9 ++
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 11 +++
 arch/arm64/kvm/hyp/nvhe/pkvm.c                |  8 +-
 arch/arm64/kvm/hyp/pgtable.c                  |  5 +-
 arch/arm64/kvm/mmu.c                          |  4 +-
 12 files changed, 126 insertions(+), 10 deletions(-)