linux-toradex.git/tools/testing/selftests/kvm/arm64/hidden_features.c, branch master Linux kernel for Apalis and Colibri modules KVM: arm64: selftests: Check a feature hidden in an ID register is UNDEF 2026-09-29T16:08:56+00:00 Fuad Tabba fuad.tabba@linux.dev 2026-09-29T09:00:31+00:00 afb4334fb52c7b416bbc9c4b166f6806509f734b Userspace can hide a feature from a guest by clearing its field in a writable ID register, and KVM then makes the feature's instructions UNDEFINED in the guest by trapping or disabling them. No selftest checks that. Add a test that runs the instruction of each of TLBI OS, MOPS, TCR2_EL1 and FPMR once with its field as advertised and once with it cleared, and expects an UNDEF only when cleared. A feature the vCPU doesn't advertise is skipped, as is hidden TLBI OS on a CPU with neither FGT nor FEAT_EVT2, where KVM can't trap it. Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev> Link: https://patch.msgid.link/20260929090031.3829185-5-fuad.tabba@linux.dev Signed-off-by: Oliver Upton <oupton@kernel.org> 
Userspace can hide a feature from a guest by clearing its field in a
writable ID register, and KVM then makes the feature's instructions
UNDEFINED in the guest by trapping or disabling them. No selftest checks
that.

Add a test that runs the instruction of each of TLBI OS, MOPS, TCR2_EL1
and FPMR once with its field as advertised and once with it cleared, and
expects an UNDEF only when cleared. A feature the vCPU doesn't advertise
is skipped, as is hidden TLBI OS on a CPU with neither FGT nor
FEAT_EVT2, where KVM can't trap it.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260929090031.3829185-5-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>