[PATCH 0/2] KVM: arm64: Fix and test MMIO sign-extending loads

[Fuad Tabba <fuad.tabba@linux.dev>]

Hi folks,

A sign-extending load (LDRSB/LDRSH/LDRSW) from emulated MMIO returns a
zero-extended value rather than the sign-extended one the architecture
requires; vcpu_data_host_to_guest() strips the sign bits when it masks
the data to the access width.

If my git archeology is right, the masking dates to 2014 (b30070862edbd,
big-endian support) and has been wrong ever since, but sign-extending
loads from device memory are rare enough that nobody hit it. Patch 1
fixes it; patch 2 adds a selftest so it doesn't regress.

Cheers,
/fuad

Fuad Tabba (2):
  KVM: arm64: Fix sign-extension of MMIO loads
  KVM: arm64: selftests: Add MMIO sign-extending load test

 arch/arm64/kvm/mmio.c                         |   7 +-
 tools/testing/selftests/kvm/Makefile.kvm      |   1 +
 .../selftests/kvm/arm64/mmio_sign_ext.c       | 133 ++++++++++++++++++
 3 files changed, 138 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/arm64/mmio_sign_ext.c


base-commit: 8cd9520d35a6c38db6567e97dd93b1f11f185dc6
-- 
2.39.5