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

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Date:   Fri, 5 Mar 2021 09:04:20 +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 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

Thanks,
Laurent.