s390/cpumf: rework program parameter setting to detect guest samples

The program parameter can be used to mark hardware samples with
some token.  Previously, it was used to mark guest samples only.

Improve the program parameter doubleword by combining two parts,
the leftmost LPP part and the rightmost PID part.  Set the PID
part for processes by using the task PID.
To distinguish host and guest samples for the kernel (PID part
is zero), the guest must always set the program paramater to a
non-zero value.  Use the leftmost bit in the LPP part of the
program parameter to be able to detect guest kernel samples.

[brueckner@linux.vnet.ibm.com]: Split __LC_CURRENT and introduced
__LC_LPP. Corrected __LC_CURRENT users and adjusted assembler parts.
And updated the commit message accordingly.

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

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index b973972f6ba5..3d8da1e742c2 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -1019,11 +1019,13 @@ static int perf_push_sample(struct perf_event *event, struct sf_raw_sample *sfr)
 		break;
 	}
 
-	/* The host-program-parameter (hpp) contains the pid of
-	 * the CPU thread as set by sie64a() in entry.S.
-	 * If non-zero assume a guest sample.
+	/*
+	 * A non-zero guest program parameter indicates a guest
+	 * sample.
+	 * Note that some early samples might be misaccounted to
+	 * the host.
 	 */
-	if (sfr->basic.hpp)
+	if (sfr->basic.gpp)
 		sde_regs->in_guest = 1;
 
 	overflow = 0;