Messages in this thread | | | Subject | Re: [PATCH] irqchip/gic-v3-its: Add early memory allocation errata | From | Marc Zyngier <> | Date | Fri, 5 Oct 2018 14:42:32 +0100 |
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On 05/10/18 13:33, Matthias Brugger wrote: > > > On 05/10/2018 12:55, Marc Zyngier wrote: >> Hi Matthias, >> >> On 04/10/18 23:11, Matthias Brugger wrote: >>> Friendly reminder, if anyone has any comment on the patch :) >>> >>> On 9/12/18 11:52 AM, matthias.bgg@kernel.org wrote: >>>> From: Matthias Brugger <mbrugger@suse.com> >>>> >>>> Some hardware does not implement two-level page tables so that >>>> the amount of contigious memory needed by the baser is bigger >>>> then the zone order. This is a known problem on Cavium Thunderx >>>> with 4K page size. >>>> >>>> We fix this by adding an errata which allocates the memory early >>>> in the boot cycle, using the memblock allocator. >>>> >>>> Signed-off-by: Matthias Brugger <mbrugger@suse.com> >>>> --- >>>> arch/arm64/Kconfig | 12 ++++++++ >>>> arch/arm64/include/asm/cpucaps.h | 3 +- >>>> arch/arm64/kernel/cpu_errata.c | 33 +++++++++++++++++++++ >>>> drivers/irqchip/irq-gic-v3-its.c | 50 ++++++++++++++++++++------------ >>>> 4 files changed, 79 insertions(+), 19 deletions(-) >> >> My only comment would be to state how much I dislike both the HW and the >> patch... ;-) The idea that we have some erratum that depends on the page size >> doesn't feel good at all. >> > > Well ugly HW needs ugly patches ;-) > >>>> >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>>> index 1b1a0e95c751..dfd9fe08f0b2 100644 >>>> --- a/arch/arm64/Kconfig >>>> +++ b/arch/arm64/Kconfig >>>> @@ -597,6 +597,18 @@ config QCOM_FALKOR_ERRATUM_E1041 >>>> If unsure, say Y. >>>> +config CAVIUM_ALLOC_ITS_TABLE_EARLY >>>> + bool "Cavium Thunderx: Allocate the its table early" >>>> + default y >>>> + depends on ARM64_4K_PAGES && FORCE_MAX_ZONEORDER < 13 >> >> Here's a though: Why don't we ensure that FORCE_MAX_ZONEORDER is such as we >> could always allocate the same amount of memory, no matter what the page size >> is? That, or bump FORCE_MAX_ZONEORDER to 13 if the kernel includes support for TX1. >> > > Bumping FORCE_MAX_ZONEORDER when TX1 is supported was proposed here: > https://patchwork.kernel.org/patch/6322281/ > > To bring in some more history, the CMA approach ended with this discussion: > https://patchwork.kernel.org/patch/9888041/ > >> Any of this of course requires buy-in from the arm64 maintainers, as this is >> quite a departure from the way things work so far. >> > > With my distribution head on, I would prefer a solution that does not change > FORCE_MAX_ZONEORDER. That's how I came to the idea providing a third solution to > the same problem :)
Why is that a problem? What impact does this have on your favourite distro?
Thanks,
M. -- Jazz is not dead. It just smells funny...
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