Michal Suchánek <msucha...@suse.de> writes: > On Tue, 01 May 2018 21:11:06 +1000 > Michael Ellerman <m...@ellerman.id.au> wrote: >> Michal Suchánek <msucha...@suse.de> writes: >> > On Tue, 24 Apr 2018 14:15:57 +1000 >> > Michael Ellerman <m...@ellerman.id.au> wrote: >> > >> >> From: Michal Suchanek <msucha...@suse.de> >> >> >> >> Check what firmware told us and enable/disable the barrier_nospec >> >> as appropriate. >> >> >> >> We err on the side of enabling the barrier, as it's no-op on older >> >> systems, see the comment for more detail. >> >> >> >> Signed-off-by: Michael Ellerman <m...@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. > > Right, I was looking at an older implementation which turned off both > v1 and v2 with same parameter. In current kernel the v1 mitigation is > not turned off at all.
Ah OK. >> Which is not to say we can't add one, but I wasn't sure if it was >> really worth it. > > The current thinking is that most performance relevant cases are > covered with array_nospec which has little overhead. The less code we > have for this the better ;-) Amen to that :) cheers
