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authorChristian Borntraeger <borntraeger@de.ibm.com>2016-02-29 16:05:35 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2016-03-02 06:44:28 -0600
commitb1685ab9bd3ae14830acac8ffdc7aafc0fb416e3 (patch)
treee8d21a1c7ed7e37ca67fa0ee160b2df0d9ad5fcc /arch/s390
parent5d7eccecf8621e3cf5adcec9cf80aa444b4610d4 (diff)
downloadop-kernel-dev-b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3.zip
op-kernel-dev-b1685ab9bd3ae14830acac8ffdc7aafc0fb416e3.tar.gz
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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/kernel/entry.S1
-rw-r--r--arch/s390/kernel/perf_cpum_sf.c9
2 files changed, 7 insertions, 3 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index cd5a191..4ba688c 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 3d8da1e..1a43474 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;
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