Michal Such=C3=A1nek [off-list ref] writes:

Hello,

On Tue, 24 Apr 2018 14:15:57 +1000
Michael Ellerman [off-list ref] wrote:

quoted

From: Michal Suchanek <redacted>
=20
Check what firmware told us and enable/disable the barrier_nospec as
appropriate.
=20
We err on the side of enabling the barrier, as it's no-op on older
systems, see the comment for more detail.
=20
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

...

I am missing the option for the barrier to be disabled by a kernel
commandline argument here.

It does make sense to add a kernel parameter that is checked on boot to
be compatible with other platforms that implement one.

No other platforms have an option to disable variant 1 mitigations, so
there isn't an existing parameter we can use.

Which is not to say we can't add one, but I wasn't sure if it was really
worth it.

But I guess we should add one, I might do it as a follow-up patch.

cheers