On Wed, Nov 29, 2017 at 02:23:43PM +1000, Nicholas Piggin wrote: > On Wed, 29 Nov 2017 15:06:52 +1100 > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > a3b2cb30 "powerpc: Do not call ppc_md.panic in fadump panic notifier" > > purports to fix a problem when the kernel panics with fadump not > > registered, but it breaks something else instead. I _think_ it was > > working on the incorrect assumption that ppc_md.panic was (or should > > be) only used with fadump, but I'm not really sure. > > > > Panic works with kdump enabled, and (I think) with fadump enabled). > > However, with neither of these enabled, we always go to the generic > > panic logic. > > Yeah thanks, I can't remember what assumption I was working on tbh. > > > That's incorrect for PAPR guests - they should call ibm,os-term via > > RTAS. Under qemu this leads to a "GUEST_PANICKED" event notification > > which higher-level management pays attention to. Since a3b2cb30 we > > now reboot instead of reporting that. > > > > I believe it will also break panic for PS3 machines, but since that > > platform basically no longer exists, we probably don't care. > > I (hope) it should just go down to the normal panic path and not do > much worse than it already does -- although it won't print out that > message. > > > I'm not entirely sure how to fix this. I _think_ what we want is to > > call ppc_md.panic from a late panic notifier, the way this patch does > > for fadump_panic_event() if fadump is registered. > > The problem I had there is that some of the printk and console stuff > wasn't getting flushed out, so I was getting a blank screen. This was > probably in conjunction with panicing from NMI context that we're now > starting to introduce. > > So it's a bit annoying. There's other ugliness we have for being unable > to control panic code well enough from arch code > (arch/powerpc/platforms/powernv/opal.c) > > I guess a really minimal fix is to put an #ifdef powerpc down the bottom > there (/me *cries*).
Um.. right. I'm not really sure from that how to go forward from here. We want to fix this for RHEL7.5, which doesn't give us a lot of time. Adding the #ifdef at the bottom of the generic panic code is gross, but there's already a bunch of that, so maybe adequate until a better solution can be found? -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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