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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2016-02-29 16:05:35 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-03-02 06:44:28 -0600 |
| commit | b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3 (patch) | |
| tree | e8d21a1c7ed7e37ca67fa0ee160b2df0d9ad5fcc | |
| parent | 5d7eccecf8621e3cf5adcec9cf80aa444b4610d4 (diff) | |
| download | linux-b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3.tar.gz linux-b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3.tar.bz2 linux-b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3.zip | |
s390/cpumf: Improve guest detection heuristics
commit e22cf8ca6f75 ("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>
| -rw-r--r-- | arch/s390/kernel/entry.S | 1 | ||||
| -rw-r--r-- | arch/s390/kernel/perf_cpum_sf.c | 9 |
2 files changed, 7 insertions, 3 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index cd5a191381b9..4ba688c9d5a6 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -186,6 +186,7 @@ ENTRY(__switch_to) stg %r5,__LC_THREAD_INFO # store thread info of next stg %r15,__LC_KERNEL_STACK # store end of kernel stack lg %r15,__THREAD_ksp(%r1) # load kernel stack of next + /* c4 is used in guest detection: arch/s390/kernel/perf_cpum_sf.c */ lctl %c4,%c4,__TASK_pid(%r3) # load pid to control reg. 4 mvc __LC_CURRENT_PID(4,%r0),__TASK_pid(%r3) # store pid of next lmg %r6,%r15,__SF_GPRS(%r15) # load gprs of next task diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c index 3d8da1e742c2..1a43474df541 100644 --- a/arch/s390/kernel/perf_cpum_sf.c +++ b/arch/s390/kernel/perf_cpum_sf.c @@ -1022,10 +1022,13 @@ static int perf_push_sample(struct perf_event *event, struct sf_raw_sample *sfr) /* * A non-zero guest program parameter indicates a guest * sample. - * Note that some early samples might be misaccounted to - * the host. + * Note that some early samples or samples from guests without + * lpp usage would be misaccounted to the host. We use the asn + * value as a heuristic to detect most of these guest samples. + * If the value differs from the host hpp value, we assume + * it to be a KVM guest. */ - if (sfr->basic.gpp) + if (sfr->basic.gpp || sfr->basic.prim_asn != (u16) sfr->basic.hpp) sde_regs->in_guest = 1; overflow = 0; |