en Copyright 2015 Java http://kernelsources.org:8080/source/history/linux/tools/testing/selftests/kvm/arm64/hidden_features.c#afb4334fb52c7b416bbc9c4b166f6806509f734b KVM: arm64: selftests: Check a feature hidden in an ID register is UNDEFUserspace can hide a feature from a guest by clearing its field in awritable ID register, and KVM then makes the feature's instructionsUNDEFINED in the guest by trapping or disabling them. No selftest checksthat.Add a test that runs the instruction of each of TLBI OS, MOPS, TCR2_EL1and FPMR once with its field as advertised and once with it cleared, andexpects an UNDEF only when cleared. A feature the vCPU doesn't advertiseis skipped, as is hidden TLBI OS on a CPU with neither FGT norFEAT_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.devSigned-off-by: Oliver Upton <oupton@kernel.org> List of files: /linux/tools/testing/selftests/kvm/arm64/hidden_features.c Tue, 29 Sep 2026 11:00:31 +0200 Fuad Tabba <fuad.tabba@linux.dev>