Hi Mark, On Fri, 2014-05-09 at 09:44 +0100, Mark Rutland wrote: > On Fri, May 09, 2014 at 01:48:17AM +0100, Geoff Levand wrote: > > + /* If we have the cup_ops use them. */ > > + > > + if (cpu_ops[cpu]->cpu_disable && cpu_ops[cpu]->cpu_die > > + && !cpu_ops[cpu]->cpu_disable(cpu)) > > + cpu_ops[cpu]->cpu_die(cpu); > > For PSCI 0.2 support, we're going to need a cpu_kill callback which we > can't call from the dying CPU. Specifically, we'll need to poll > CPU_AFFINITY_INFO to ensure that secondaries have _actually_ left the > kernel and aren't going to be adversely affected by the kernel text > getting clobbered. > > As we're going to wire that up to the cpu hotplug infrastructure it > would be nice to perform the hotplug for kexec by reusing the generic > hotplug infrastructure rather than calling portions of the arm64 > implementation directly. OK, is there somewhere I can see that new code, and when do you expect it to be merged? > > + > > + /* Spin here if the cup_ops fail. */ > > + > > while (1) > > cpu_relax(); > > This seems very dodgy to me. If a CPU doesn't actually die it's going to > be spinning in some memory that we may later clobber. At that point the > CPU will do arbitrarily bad things when it begins executing whatever its > currently executing instructions (or vectors) were replaced by, and you > will waste hours trying to figure out what went wrong (See 8121cf312a19 > "ARM: 7766/1: versatile: don't mark pen as __INIT" for a similar mess). > > If we fail to hotplug a CPU we at minimum need some acknowledgement that > we failed. I would rather we failed to kexec entirely in that case. This loop is for the non-hotplug power-off shutdown. This whole smp_stop support needs to be reconsidered for a hotplug spin-table re-work. -Geoff
