On 09/05/16 16:10, Marc Zyngier wrote: > On 09/05/16 14:13, Jon Hunter wrote: >> On 09/05/16 13:23, Marc Zyngier wrote: [snip] >>> This patch have the effect of making misconfigured PPIs absolutely >>> obvious. I still need to wrap my head around the root cause, but here's >>> the findings I have so far: >>> >>> - kvmtool generates a DT with the wrong trigger information (edge >>> instead of level) for the timer. >>> - with this patch applied, "cyclictest -S" reliably locks up when run in >>> a guest (missing a timer interrupt, goodbye CPU). >>> - Either fixing kvmtool or reverting that patch makes it work reliably >>> again. >>> >>> My gut feeling is that until that patch, the failing irq_set_irq_type() >>> wasn't affecting the kernel's view of the trigger (it was still treated >>> as level). With this patch, the kernel now trusts whatever is coming >>> from the firmware, and the misconfiguration becomes obvious. And just >>> grepping through the DT files for arm and arm64 sends makes me thing >>> "Holly effin' crap!". >>> >>> I'm not saying that we shouldn't perform this change though. But it is >>> quite obvious that it is going to break an awful lot of existing code >>> and platforms. I'm also cooking a small patch for the arch timer (which >>> seems to be described in DT with a fairly high level of brokenness), so >>> that we can mop-up most of the brain damage. >> >> Hmmm ... yes I see. I wonder if we should make the setting of the type >> here dependent upon PM being enabled for an irqchip? We could check to >> see if the .parent_device is populated and if so only then save the type >> and otherwise just set it as we do today. > > I don't really like the idea of having multiple code paths for the same thing. > This is very error prone, and likely to bitrot pretty quickly. True. However, we really need this change for irqchips and runtime-pm. So to confirm what are you suggesting we do? We could add a WARN around irq_set_irq_type() in irq_create_fwspec_mapping() for v4.7 and see how many complaints we get :-) >> We could add a WARN to the existing irq_set_irq_type() or may be just a >> pr_warn() if a WARN is too verbose so people can fix up any issues. >> >> I am also wondering if patch 4/17 "iqdomain: Fix handling of type >> settings for existing mappings" could generate a lot of reports >> interrupts failing due to bad firmware? I wonder if I should tone this >> patch down to a warning message as well as opposed to a complete failure. > > We'll see. We can always tone it down a notch, should it prove to be too noisy... > So far, I haven't seen it firing. On the other hand, I get the following stuff > on my APM board: > > [ 0.000000] GIC: PPI0 is either secure or misconfigured > [ 0.000000] GIC: PPI13 is either secure or misconfigured > [ 0.000000] arm_arch_timer: WARNING: Invalid trigger for IRQ1, assuming level low > [ 0.000000] arm_arch_timer: WARNING: Please fix your firmware > [ 0.000000] arm_arch_timer: WARNING: Invalid trigger for IRQ2, assuming level low > [ 0.000000] arm_arch_timer: WARNING: Please fix your firmware > > Pretty awesome... Indeed. Jon -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
