[PATCH 0/4] KVM: arm64: Fix host access to the EL2 stacks

[Fuad Tabba]

Hi folks,

The per-CPU EL2 stacks are initialised as host-owned after pKVM init.
fix_host_ownership() walks only the linear-map alias of each memblock
region, and the stacks, mapped in the private VA range for their guard
pages, have none.

Patch 1 is the fix, and it needs none of the other three. Patch 4 adds
the check that would have caught it and would catch similar instances
in the future: once the transfer is done, walk the private VA range and
fail init unless every valid leaf is hyp-owned, or is hyp text mapped
without write access.

Patch 2 is a fix in its own right, but to a different bug.
fix_host_ownership_walker() matches hyp text on its stage-1 permissions,
and that test hasn't matched on a non-hVHE host since 7.0, so hyp text
is donated there rather than left read-only. Nothing crashes, but the
instruction dump on hyp panic reads a page the host can't access, so
the Code: line comes out as question marks. It matches by physical
address instead, which is what patch 4 needs too. Patch 3 splits the
start of the range from the allocation cursor, with no functional
change, so patch 4 knows where the range begins.

Based on Linux 7.3-rc2 (df2908090cda3).

Cheers,
/fuad

Fuad Tabba (4):
  KVM: arm64: Transfer the hyp stack pages out of the host stage-2
  KVM: arm64: Match hyp text by physical address in fix_host_ownership()
  KVM: arm64: Move the private VA allocation cursor to __io_map_next
  KVM: arm64: Check every private mapping is hyp-owned at pKVM init

 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  2 +
 arch/arm64/kvm/hyp/include/nvhe/mm.h          |  1 +
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 20 +++++
 arch/arm64/kvm/hyp/nvhe/mm.c                  | 79 ++++++++++++++++---
 arch/arm64/kvm/hyp/nvhe/setup.c               | 16 +++-
 5 files changed, 108 insertions(+), 10 deletions(-)


base-commit: df2908090cda368b01ff43709f51890076c56157
-- 
2.39.5