4.13-stable review patch. If anyone has any objections, please let me know.
------------------ From: Martin Schwidefsky <[email protected]> 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 <[email protected]> Signed-off-by: Martin Schwidefsky <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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
