arm64: Use the clearbhb instruction in mitigations

Future CPUs may implement a clearbhb instruction that is sufficient
to mitigate SpectreBHB. CPUs that implement this instruction, but
not CSV2.3 must be affected by Spectre-BHB.

Add support to use this instruction as the BHB mitigation on CPUs
that support it. The instruction is in the hint space, so it will
be treated by a NOP as older CPUs.

Reviewed-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: James Morse <[email protected]>

0 files changed, 0 insertions, 0 deletions