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    SubjectRe: [PATCH] irqchip/gic-v3-its: Add early memory allocation errata
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    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.

    >>
    >> 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.

    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.

    Thanks,

    M.
    --
    Jazz is not dead. It just smells funny...

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