4.13-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
commit 0a5e2ec2647737907d267c09dc9a25fab1468865 upstream.
The new detection code for guest machine checks added a check based
on %r11 to .Lcleanup_sie to distinguish between normal asynchronous
interrupts and machine checks. But the funtion is called from the
program check handler as well with an undefined value in %r11.
The effect is that all program exceptions pointing to the SIE instruction
will set the CIF_MCCK_GUEST bit. The bit stays set for the CPU until the
next machine check comes in which will incorrectly be interpreted as a
guest machine check.
The simplest fix is to stop using .Lcleanup_sie in the program check
handler and duplicate a few instructions.
Fixes: c929500d7a5a ("s390/nmi: s390: New low level handling for machine check happening in guest")
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/kernel/entry.S | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -521,12 +521,15 @@ ENTRY(pgm_check_handler)
tmhh %r8,0x0001 # test problem state bit
jnz 2f # -> fault in user space
#if IS_ENABLED(CONFIG_KVM)
- # cleanup critical section for sie64a
+ # cleanup critical section for program checks in sie64a
lgr %r14,%r9
slg %r14,BASED(.Lsie_critical_start)
clg %r14,BASED(.Lsie_critical_length)
jhe 0f
- brasl %r14,.Lcleanup_sie
+ lg %r14,__SF_EMPTY(%r15) # get control block pointer
+ ni __SIE_PROG0C+3(%r14),0xfe # no longer in SIE
+ lctlg %c1,%c1,__LC_USER_ASCE # load primary asce
+ larl %r9,sie_exit # skip forward to sie_exit
#endif
0: tmhh %r8,0x4000 # PER bit set in old PSW ?
jnz 1f # -> enabled, can't be a double fault