[PATCH 4/4] powerpc/powernv: Remove POWER9 PVR version check for entry and uaccess flushes

[Joel Stanley]

On Tue, 4 May 2021 at 09:16, Nicholas Piggin <npiggin at gmail.com> wrote:
>
> Excerpts from Joel Stanley's message of May 4, 2021 10:51 am:
> > On Mon, 3 May 2021 at 13:04, Nicholas Piggin <npiggin at gmail.com> wrote:
> >>
> >> These aren't necessarily POWER9 only, and it's not to say some new
> >> vulnerability may not get discovered on other processors for which
> >> we would like the flexibility of having the workaround enabled by
> >> firmware.
> >>
> >> Remove the restriction that they only apply to POWER9.
> >
> > I was wondering how these worked which led me to reviewing your patch.
> > From what I could see, these are enabled by default (SEC_FTR_DEFAULT
> > in arch/powerpc/include/asm/security_features.h), so unless all
> > non-POWER9 machines have set the "please don't" bit in their firmware
> > this patch will enable the feature for those machines. Is that what
> > you wanted?
>
> Yes. POWER7/8 should be affected (it's similar mechanism that requires
> the meltdown RFI flush, which those processors need).
>
> POWER10 we haven't released a bare metal firmware with the right bits
> yet. Not urgent at the moment but wouldn't hurt to specify them and
> add the Linux code for them.

Thanks for the explanation. This could go in the commit message if you re-spin.

Reviewed-by: Joel Stanley <joel at jms.id.au>