s390/cpumf: Fix lpp detection

commit 7a76aa95f6f6682db5629449d763251d1c9f8c4e upstream.

we have to check bit 40 of the facility list before issuing LPP
and not bit 48. Otherwise a guest running on a system with
"The decimal-floating-point zoned-conversion facility" and without
the "The set-program-parameters facility" might crash on an lpp
instruction.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: e22cf8ca6f75 ("s390/cpumf: rework program parameter setting to detect guest samples")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 58b719fa8067a5b7e2ec428c0babc758c6dc0eb4..1ad2407c7f7590fea27a8e94d541be5179161602 100644 (file)
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -16,7 +16,7 @@
 
 __HEAD
 ENTRY(startup_continue)
-       tm      __LC_STFL_FAC_LIST+6,0x80       # LPP available ?
+       tm      __LC_STFL_FAC_LIST+5,0x80       # LPP available ?
        jz      0f
        xc      __LC_LPP+1(7,0),__LC_LPP+1      # clear lpp and current_pid
        mvi     __LC_LPP,0x80                   #   and set LPP_MAGIC