From: Alexander Gordeev agordeev@linux.ibm.com
[ Upstream commit dc2ab23b992c9d5dab93b9bf01b10b10465e537e ]
Macro mem_assign_absolute() is used to initialize a target CPU lowcore callback parameters. But despite the macro name it writes to the absolute lowcore only if the target CPU is offline. In case the CPU is online the macro does implicitly write to the normal memory.
That behaviour is correct, but extremely subtle. Sacrifice few program bits in favour of clarity and distinguish between online vs offline CPUs and normal vs absolute lowcore pointer.
Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/smp.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index e57eb2260b90..982b72ca677c 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -328,10 +328,17 @@ static void pcpu_delegate(struct pcpu *pcpu, /* Stop target cpu (if func returns this stops the current cpu). */ pcpu_sigp_retry(pcpu, SIGP_STOP, 0); /* Restart func on the target cpu and stop the current cpu. */ - mem_assign_absolute(lc->restart_stack, stack); - mem_assign_absolute(lc->restart_fn, (unsigned long) func); - mem_assign_absolute(lc->restart_data, (unsigned long) data); - mem_assign_absolute(lc->restart_source, source_cpu); + if (lc) { + lc->restart_stack = stack; + lc->restart_fn = (unsigned long)func; + lc->restart_data = (unsigned long)data; + lc->restart_source = source_cpu; + } else { + mem_assign_absolute(lc->restart_stack, stack); + mem_assign_absolute(lc->restart_fn, (unsigned long)func); + mem_assign_absolute(lc->restart_data, (unsigned long)data); + mem_assign_absolute(lc->restart_source, source_cpu); + } __bpon(); asm volatile( "0: sigp 0,%0,%2 # sigp restart to target cpu\n"