[Skiboot] [PATCH v3 0/5] CAPI disabling support for kexec/fast reboot

Stewart Smith stewart at linux.vnet.ibm.com
Mon Mar 20 16:02:44 AEDT 2017

Andrew Donnellan <andrew.donnellan at au1.ibm.com> writes:
> On 27/01/17 18:33, Andrew Donnellan wrote:
>> Currently, if you attempt to kexec or fast reboot from a machine with a
>> CAPI card and the cxl driver loaded, you are going to have an exceedingly
>> bad time. It turns out that the hardware doesn't really cope very well with
>> going through the standard Linux PCI initialisation process while a PHB is
>> still in CAPI mode. Checkstops everywhere!
>> This series implements support for switching a PHB from CAPI mode back to
>> regular PCIe mode during a complete reset. The SCOM sequences have been
>> derived through a mix of advice from other IBMers, reading through various
>> internal workbooks, and trial and error.
>> This has only been lightly tested - I've kexec-ed/fast rebooted quite a few
>> times with no real problems, and I've run some basic CAPI tests that don't
>> seem to fail too much more than they normally fail. As this procedure
>> involves forcing the CAPP into recovery, we do see a lot of HMIs but as far
>> as I'm aware they're harmless and there's not much we can really do about
>> them.
>> At this stage, I haven't thought too hard about whether we can
>> disable CAPI mode while Linux is running for e.g. PCI hotplug, which could
>> get tricky. That's a question for later...
>> Thanks to Vaibhav Jain (who made a previous attempt at this), Mikey
>> Neuling, Ben Herrenschmidt, Gavin Shan, Bill Daly, Ken Lauricella and JT
>> Kellington for advice on various bits of this.
> Stewart - thoughts on merging this?

Yes, I just merged it to master as of ddb880fee274924f5f7307686b7ff30a2f04e432


I ran a weekend of (fast) reboot loop testing, and I'm pretty sure the issues I
hit were not related to this patchset

Stewart Smith
OPAL Architect, IBM.

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