linux-kernel - Re: [PATCH] powerpc/pseries: export LPAR security flavor in lparcfg

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Message-ID: <87wnulrfk4.fsf@mpe.ellerman.id.au>
Date:   Fri, 05 Mar 2021 22:43:55 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Laurent Dufour <ldufour@...ux.ibm.com>, benh@...nel.crashing.org,
        paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org
Cc:     nathanl@...ux.ibm.com, cheloha@...ux.ibm.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/pseries: export LPAR security flavor in lparcfg

Laurent Dufour <ldufour@...ux.ibm.com> writes:
> Le 05/03/2021 à 07:23, Michael Ellerman a écrit :
>> Laurent Dufour <ldufour@...ux.ibm.com> writes:
>>> This is helpful to read the security flavor from inside the LPAR.
>> 
>> We already have /sys/kernel/debug/powerpc/security_features.
>> 
>> Is that not sufficient?
>
> Not really, it only reports that security mitigation are on or off but not the 
> level set through the ASMI menu. Furthermore, reporting it through
> /proc/powerpc/lparcfg allows an easy processing by the lparstat command (see below).
>
>> 
>>> Export it like this in /proc/powerpc/lparcfg:
>>>
>>> $ grep security_flavor /proc/powerpc/lparcfg
>>> security_flavor=1
>>>
>>> Value means:
>>> 0 Speculative execution fully enabled
>>> 1 Speculative execution controls to mitigate user-to-kernel attacks
>>> 2 Speculative execution controls to mitigate user-to-kernel and
>>>    user-to-user side-channel attacks
>> 
>> Those strings come from the FSP help, but we have no guarantee it won't
>> mean something different in future.
>
> I think this is nailed down, those strings came from:
> https://www.ibm.com/support/pages/node/715841
>
> Where it is written (regarding AIX):
>
> On an LPAR, one can use lparstat -x to display the current mitigation mode:
> 0 = Speculative execution fully enabled
> 1 = Speculative execution controls to mitigate user-to-kernel side-channel attacks
> 2 = Speculative execution controls to mitigate user-to-kernel and user-to-user 
> side-channel attacks
>
> We have been requested to provide almost the same, which I proposed in 
> powerpc-utils:
> https://groups.google.com/g/powerpc-utils-devel/c/NaKXvdyl_UI/m/wa2stpIDAQAJ

OK. Do you mind sending a v2 with all those details incorporated into
the change log?

cheers