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

Le 05/03/2021 à 07:23, Michael Ellerman a écrit :

Laurent Dufour [off-list ref] writes:

quoted

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).

quoted

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.