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

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Message-ID: <c0b69e16-3b4c-7a27-f3ca-eba1eff5624a@linux.ibm.com>
Date:   Fri, 5 Mar 2021 12:45:14 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>, 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

Le 05/03/2021 à 12:43, Michael Ellerman a écrit :
> 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?

Ok will do so.

Thanks