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    SubjectRe: [PATCH v12 0/9] support reserving crashkernel above 4G on arm64 kdump
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    On 9/7/20 8:47 AM, Chen Zhou wrote:
    > There are following issues in arm64 kdump:
    > 1. We use crashkernel=X to reserve crashkernel below 4G, which
    > will fail when there is no enough low memory.
    > 2. If reserving crashkernel above 4G, in this case, crash dump
    > kernel will boot failure because there is no low memory available
    > for allocation.
    > 3. Since commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32"),
    > if the memory reserved for crash dump kernel falled in ZONE_DMA32,
    > the devices in crash dump kernel need to use ZONE_DMA will alloc
    > fail.
    >
    > To solve these issues, change the behavior of crashkernel=X.
    > crashkernel=X tries low allocation in DMA zone, and fall back to
    > high allocation if it fails.
    > If requized size X is too large and leads to very little low memory
    > in DMA zone after low allocation, the system may not work normally.
    > So add a threshold and go for high allocation directly if the required
    > size is too large. The value of threshold is set as the half of
    > the low memory.
    >
    > We can also use "crashkernel=X,high" to select a high region above
    > DMA zone, which also tries to allocate at least 256M low memory in
    > DMA zone automatically.
    > "crashkernel=Y,low" can be used to allocate specified size low memory.
    > For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone.
    >
    > When reserving crashkernel in high memory, some low memory is reserved
    > for crash dump kernel devices. So there may be two regions reserved for
    > crash dump kernel.
    > In order to distinct from the high region and make no effect to the use
    > of existing kexec-tools, rename the low region as "Crash kernel (low)",
    > and pass the low region by reusing DT property
    > "linux,usable-memory-range". We made the low memory region as the last
    > range of "linux,usable-memory-range" to keep compatibility with existing
    > user-space and older kdump kernels.
    >
    > Besides, we need to modify kexec-tools:
    > arm64: support more than one crash kernel regions(see [1])
    >
    > Another update is document about DT property 'linux,usable-memory-range':
    > schemas: update 'linux,usable-memory-range' node schema(see [2])
    >
    > This patchset contains the following nine patches:
    > 0001-x86-kdump-move-CRASH_ALIGN-to-2M.patch
    > 0002-x86-kdump-make-the-lower-bound-of-crash-kernel-reser.patch
    > 0003-x86-kdump-use-macro-CRASH_ADDR_LOW_MAX-in-functions-.patch
    > 0004-x86-kdump-move-reserve_crashkernel-_low-into-crash_c.patch
    > 0005-arm64-kdump-introduce-some-macroes-for-crash-kernel-.patch
    > 0006-arm64-kdump-reimplement-crashkernel-X.patch
    > 0007-kdump-add-threshold-for-the-required-memory.patch
    > 0008-arm64-kdump-add-memory-for-devices-by-DT-property-li.patch
    > 0009-kdump-update-Documentation-about-crashkernel.patch
    >
    > 0001-0003 are some x86 cleanups which prepares for making
    > functionsreserve_crashkernel[_low]() generic.
    >
    > 0004 makes functions reserve_crashkernel[_low]() generic.
    > 0005-0006 reimplements crashkernel=X.
    > 0007 adds threshold for the required memory.
    > 0008 adds memory for devices by DT property linux,usable-memory-range.
    > 0009 updates the doc.
    >
    > Changes since [v11]
    > - Rebased on top of 5.9-rc4.
    > - Make the function reserve_crashkernel() of x86 generic.
    > Suggested by Catalin, make the function reserve_crashkernel() of x86 generic
    > and arm64 use the generic version to reimplement crashkernel=X.
    >
    > Changes since [v10]
    > - Reimplement crashkernel=X suggested by Catalin, Many thanks to Catalin.
    >
    > Changes since [v9]
    > - Patch 1 add Acked-by from Dave.
    > - Update patch 5 according to Dave's comments.
    > - Update chosen schema.
    >
    > Changes since [v8]
    > - Reuse DT property "linux,usable-memory-range".
    > Suggested by Rob, reuse DT property "linux,usable-memory-range" to pass the low
    > memory region.
    > - Fix kdump broken with ZONE_DMA reintroduced.
    > - Update chosen schema.
    >
    > Changes since [v7]
    > - Move x86 CRASH_ALIGN to 2M
    > Suggested by Dave and do some test, move x86 CRASH_ALIGN to 2M.
    > - Update Documentation/devicetree/bindings/chosen.txt.
    > Add corresponding documentation to Documentation/devicetree/bindings/chosen.txt
    > suggested by Arnd.
    > - Add Tested-by from Jhon and pk.
    >
    > Changes since [v6]
    > - Fix build errors reported by kbuild test robot.
    >
    > Changes since [v5]
    > - Move reserve_crashkernel_low() into kernel/crash_core.c.
    > - Delete crashkernel=X,high.
    > - Modify crashkernel=X,low.
    > If crashkernel=X,low is specified simultaneously, reserve spcified size low
    > memory for crash kdump kernel devices firstly and then reserve memory above 4G.
    > In addition, rename crashk_low_res as "Crash kernel (low)" for arm64, and then
    > pass to crash dump kernel by DT property "linux,low-memory-range".
    > - Update Documentation/admin-guide/kdump/kdump.rst.
    >
    > Changes since [v4]
    > - Reimplement memblock_cap_memory_ranges for multiple ranges by Mike.
    >
    > Changes since [v3]
    > - Add memblock_cap_memory_ranges back for multiple ranges.
    > - Fix some compiling warnings.
    >
    > Changes since [v2]
    > - Split patch "arm64: kdump: support reserving crashkernel above 4G" as
    > two. Put "move reserve_crashkernel_low() into kexec_core.c" in a separate
    > patch.
    >
    > Changes since [v1]:
    > - Move common reserve_crashkernel_low() code into kernel/kexec_core.c.
    > - Remove memblock_cap_memory_ranges() i added in v1 and implement that
    > in fdt_enforce_memory_region().
    > There are at most two crash kernel regions, for two crash kernel regions
    > case, we cap the memory range [min(regs[*].start), max(regs[*].end)]
    > and then remove the memory range in the middle.
    >
    > [1]: https://urldefense.com/v3/__http://lists.infradead.org/pipermail/kexec/2020-June/020737.html__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BsfMsIet$
    > [2]: https://urldefense.com/v3/__https://github.com/robherring/dt-schema/pull/19__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6Bv1JxB2D$
    > [v1]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/2/1174__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BgTzrgKq$
    > [v2]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/86__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6Btz3iM8F$
    > [v3]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/306__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BuqcVDab$
    > [v4]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/15/273__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6Bgdlc1Y7$
    > [v5]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/5/6/1360__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BsuuZ6C_$
    > [v6]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/8/30/142__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6Bo4IxHqi$
    > [v7]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/12/23/411__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BjlqN_6I$
    > [v8]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/5/21/213__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BlBSztwY$
    > [v9]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/6/28/73__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BoNFCNt9$
    > [v10]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/7/2/1443__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BvfD2Ihf$
    > [v11]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/8/1/150__;!!GqivPVa7Brio!IzjRTihkWj0uY8lqf60OD7rbqIAhyGD20C4EZpBaPsNfWxuPgeU1Av-fzig6BohKxmce$
    >
    > Chen Zhou (9):
    > x86: kdump: move CRASH_ALIGN to 2M
    > x86: kdump: make the lower bound of crash kernel reservation
    > consistent
    > x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions
    > reserve_crashkernel[_low]()
    > x86: kdump: move reserve_crashkernel[_low]() into crash_core.c
    > arm64: kdump: introduce some macroes for crash kernel reservation
    > arm64: kdump: reimplement crashkernel=X
    > kdump: add threshold for the required memory
    > arm64: kdump: add memory for devices by DT property
    > linux,usable-memory-range
    > kdump: update Documentation about crashkernel
    >
    > Documentation/admin-guide/kdump/kdump.rst | 25 ++-
    > .../admin-guide/kernel-parameters.txt | 13 +-
    > arch/arm64/include/asm/kexec.h | 15 ++
    > arch/arm64/include/asm/processor.h | 1 +
    > arch/arm64/kernel/setup.c | 13 +-
    > arch/arm64/mm/init.c | 105 ++++------
    > arch/arm64/mm/mmu.c | 4 +
    > arch/x86/include/asm/kexec.h | 28 +++
    > arch/x86/kernel/setup.c | 165 +--------------
    > include/linux/crash_core.h | 4 +
    > include/linux/kexec.h | 2 -
    > kernel/crash_core.c | 192 ++++++++++++++++++
    > kernel/kexec_core.c | 17 --
    > 13 files changed, 328 insertions(+), 256 deletions(-)
    >


    I did a brief unit-test on 5.9-rc4.

    Please add:


    Tested-by: John Donnelly <John.p.donnelly@oracle.com>


    This activity is over a year old. It needs accepted.





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