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    SubjectRe: [RESEND PATCH v5 00/11] ppc64: enable kdump support for kexec_file_load syscall
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    On 07/27/2020 03:36 AM, Hari Bathini wrote:
    > Sorry! There was a gateway issue on my system while posting v5, due to
    > which some patches did not make it through. Resending...
    >
    > This patch series enables kdump support for kexec_file_load system
    > call (kexec -s -p) on PPC64. The changes are inspired from kexec-tools
    > code but heavily modified for kernel consumption.
    >
    > The first patch adds a weak arch_kexec_locate_mem_hole() function to
    > override locate memory hole logic suiting arch needs. There are some
    > special regions in ppc64 which should be avoided while loading buffer
    > & there are multiple callers to kexec_add_buffer making it complicated
    > to maintain range sanity and using generic lookup at the same time.
    >
    > The second patch marks ppc64 specific code within arch/powerpc/kexec
    > and arch/powerpc/purgatory to make the subsequent code changes easy
    > to understand.
    >
    > The next patch adds helper function to setup different memory ranges
    > needed for loading kdump kernel, booting into it and exporting the
    > crashing kernel's elfcore.
    >
    > The fourth patch overrides arch_kexec_locate_mem_hole() function to
    > locate memory hole for kdump segments by accounting for the special
    > memory regions, referred to as excluded memory ranges, and sets
    > kbuf->mem when a suitable memory region is found.
    >
    > The fifth patch moves walk_drmem_lmbs() out of .init section with
    > a few changes to reuse it for setting up kdump kernel's usable memory
    > ranges. The next patch uses walk_drmem_lmbs() to look up the LMBs
    > and set linux,drconf-usable-memory & linux,usable-memory properties
    > in order to restrict kdump kernel's memory usage.
    >
    > The seventh patch updates purgatory to setup r8 & r9 with opal base
    > and opal entry addresses respectively to aid kernels built with
    > CONFIG_PPC_EARLY_DEBUG_OPAL enabled. The next patch setups up backup
    > region as a kexec segment while loading kdump kernel and teaches
    > purgatory to copy data from source to destination.
    >
    > Patch 09 builds the elfcore header for the running kernel & passes
    > the info to kdump kernel via "elfcorehdr=" parameter to export as
    > /proc/vmcore file. The next patch sets up the memory reserve map
    > for the kexec kernel and also claims kdump support for kdump as
    > all the necessary changes are added.
    >
    > The last patch fixes a lookup issue for `kexec -l -s` case when
    > memory is reserved for crashkernel.
    >
    > Tested the changes successfully on P8, P9 lpars, couple of OpenPOWER
    > boxes, one with secureboot enabled, KVM guest and a simulator.
    >
    > v4 -> v5:
    > * Dropped patches 07/12 & 08/12 and updated purgatory to do everything
    > in assembly.
    I guess you achieve this by carefully selecting instruction to avoid
    relocation issue, right?

    Thanks,
    Pingfan

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