On 06/30/2015 01:05 PM, Rafael J. Wysocki wrote: > Hi Al, > > On Tue, Jun 30, 2015 at 8:39 PM, Al Stone <a...@redhat.com> wrote: >> On 06/30/2015 12:25 PM, Rafael J. Wysocki wrote: >>> Hi Al, >>> >>> On Tue, Jun 30, 2015 at 7:29 PM, Al Stone <a...@redhat.com> wrote: >>>> On 06/30/2015 11:07 AM, Sudeep Holla wrote: >>>>> Hi Al, >>>>> >>>>> On 18/06/15 23:36, Al Stone wrote: >>>>>> In the ACPI 5.1 version of the spec, the struct for the GICC subtable >>>>>> (struct acpi_madt_generic_interrupt) of the MADT is 76 bytes long; in >>>>>> ACPI 6.0, the struct is 80 bytes long. But, there is only one definition >>>>>> in ACPICA for this struct -- and that is the 6.0 version. Hence, when >>>>>> BAD_MADT_ENTRY() compares the struct size to the length in the GICC >>>>>> subtable, it fails if 5.1 structs are in use, and there are systems in >>>>>> the wild that have them. >>>>>> >>>>>> Note that this was found in linux-next and these patches apply against >>>>>> that tree and the arm64 kernel tree; 4.1-rc8 does not appear to have this >>>>>> problem since it still has the 5.1 struct definition. >>>>>> >>>>>> Even though there is precendent in ia64 code for ignoring the changes in >>>>>> size, this patch set instead tries to verify correctness. The first >>>>>> patch >>>>>> in the set adds macros for easily using the ACPI spec version. The >>>>>> second >>>>>> patch adds the BAD_MADT_GICC_ENTRY() macro that uses the version macros >>>>>> to >>>>>> check the GICC subtable only, accounting for the difference in >>>>>> specification >>>>>> versions that are possible. The final patch replaces BAD_MADT_ENTRY >>>>>> usage >>>>>> with the BAD_MADT_GICC_ENTRY macro in arm64 code, which is currently the >>>>>> only architecture affected. The BAD_MADT_ENTRY() will continue to work >>>>>> as >>>>>> is for all other MADT subtables. >>>>>> >>>>> >>>>> We need to get this series or a patch to remove the check(similar to >>>>> ia64) based on what Rafael prefers. Without that, platforms using ACPI >>>>> on ARM64 fails to boot with latest mainline. This blocks any testing on >>>>> ARM64/ACPI systems. >>>>> >>>>> Regards, >>>>> Sudeep >>>> >>>> I have not received any other feedback than some Reviewed-bys from >>>> Hanjun and an ACK from Will for the arm64 patch. >>>> >>>> And absolutely agreed: this is a blocker for arm64/ACPI, starting with >>>> the ACPICA 20150515 patches which appear to have gone in with 4.2-rc1. >>>> >>>> Rafael? Ping? >>> >>> I overlooked the fact that this was needed to fix a recent regression, >>> sorry about that. >>> >>> Actually, if your patch fixes an error introduced by a specific >>> commit, it is good to use the Fixes: tag to indicate that. Which I >>> still would like to do, so which commit is fixed by this? >>> >>>> Do we need these to go through your tree or the arm64 >>>> tree? Without this series (or an ia64-like solution), we have ACPI >>>> systems in the field that cannot boot. >>> >>> I'm not quite sure why the definition of BAD_MADT_GICC_ENTRY has to go >>> into include/linux/acpi.h. Why is it necessary in there? >> >> I only placed it there since it seemed to make sense, and the issue is >> generic to ACPI, not just ARM. Granted ARM is the only arch using the >> GICC subtable in MADT, > > Precisely. > >> but this is fixing how ACPICA implemented the spec, > > So that should be fixed in ACPICA eventually and linux/acpi.h is not > an ACPICA file even. > > It is possible to apply an ACPICA fix to Linux before it goes to > upstream ACPICA if it fixes a real problem in Linux. We've done > things like that.
Fair enough. I've been reluctant to add further divergence, personally. >> which in turn was ambiguous (and an errata is forthcoming to fix that). >> >> That being said, though, I'm definitely open to other possibilities. > > So I'd prefer an ACPICA fix and if that's not viable, an ARM-specific > fix to fill the gap while ACPICA is being updated. > > Thanks, > Rafael Hrm. I'll look into the ACPICA fix. I'm sure it's possible, but it may be messy. I will talk to Bob Moore and Lv Zheng about that, too. This sort of thing has surely happened before, though. In the meantime, I'll put together a new version of this patch that is ARM-specific to fill the gap. Using linux/irqchip/arm-gic-acpi.h does make sense. Thanks for all the feedback, Rafael. -- ciao, al ----------------------------------- Al Stone Software Engineer Red Hat, Inc. a...@redhat.com ----------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
