s390/cpumf: Improve guest detection heuristics

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commit e22cf8ca6f ("s390/cpumf: rework program parameter setting
to detect guest samples") requires guest changes to get proper
guest/host. We can do better: We can use the primary asn value,
which is set on all Linux variants to compare this with the host
pp value.
We now have the following cases:
1. Guest using PP
host sample:  gpp == 0, asn == hpp --> host
guest sample: gpp != 0 --> guest
2. Guest not using PP
host sample:  gpp == 0, asn == hpp --> host
guest sample: gpp == 0, asn != hpp --> guest

As soon as the host no longer sets CR4, we must back out
this heuristics - let's add a comment in switch_to.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

...

This commit is contained in:

Christian Borntraeger 2016-02-29 16:05:35 +01:00 • committed by Martin Schwidefsky

parent 5d7eccecf8

commit b1685ab9bd

2 changed files with 7 additions and 3 deletions

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1

arch/s390/kernel/entry.S

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9

arch/s390/kernel/perf_cpum_sf.c

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