Messages in this thread | | | Subject | Re: [PATCH 1/1] arm64: kexec: machine_kexec should call __flush_icache_range | From | Dave Kleikamp <> | Date | Mon, 30 Jul 2018 19:31:16 -0500 |
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On 07/30/2018 07:28 PM, AKASHI Takahiro wrote: > On Mon, Jul 30, 2018 at 04:36:28PM -0500, Dave Kleikamp wrote: >> On 07/30/2018 11:57 AM, Will Deacon wrote: >>> On Mon, Jul 30, 2018 at 11:46:24AM -0500, Dave Kleikamp wrote: >>>> On 07/30/2018 11:22 AM, Will Deacon wrote: >>>>> On Mon, Jul 30, 2018 at 05:16:42PM +0100, Catalin Marinas wrote: >>>>>> On Mon, Jul 30, 2018 at 10:29:21AM -0500, Dave Kleikamp wrote: >>>>>>> machine_kexec flushes the reboot_code_buffer from the icache >>>>>>> after stopping the other cpus. >>>>>>> >>>>>>> Commit 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache >>>>>>> for kernel mappings") added an IPI call to flush_icache_range, which >>>>>>> causes a hang here, so replace the call with __flush_icache_range >>>>>> >>>>>> While machine_kexec() may be called with interrupts disabled (IIUC) and >>>>>> we shouldn't IPI other CPUs, I don't understand why it hangs here. Are >>>>>> there any other CPUs online at this point? >>>>> >>>>> The BUG_ON and WARN_ON at the start of machine_kexec() suggest to me that >>>>> this should only happen if we're kexec'ing a crash kernel and >>>>> smp_crash_stop_failed(). Is that something we need to care about? >>>> >>>> I observed the hang trying to kexec a crash kernel and I did not see the >>>> warning that smp_crash_stop_failed(). I'm not exactly sure why >>>> flush_icache_range() hung (but it did), but I think that >>>> __flush_icache_range() makes more sense here anyway. >>> >>> Yeah, I'll pick the patch up, but it would be nice to understand the >>> failure case you observed. >> >> I see why it failed. ipi_cpu_crash_stop() does not call >> set_cpu_online(cpu, false) the way ipi_cpu_stop() does. So >> cpu_online_mask is still populated with the stopped cpus. >> >> Any reason why it isn't called there? > > Because I wanted that saved cpu-related state be as close to as it was > at panic. > If cpus go offline, the core dump would show that all the cores but > a panicked one be offline whether or not they actually were.
That makes sense.
Thanks, Dave
> > Thanks, > -Takahiro AKASHI > >> Thanks, >> Dave >> >>> >>> Will >>>
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