linux-kernel - Re: [RESEND PATCH v5 00/11] ppc64: enable kdump support for kexec_file

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Message-ID: <23911b9d-7534-031c-6f98-80f90439c834@redhat.com>
Date:   Tue, 28 Jul 2020 10:32:42 +0800
From:   piliu <piliu@...hat.com>
To:     Hari Bathini <hbathini@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     kernel test robot <lkp@...el.com>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Dave Young <dyoung@...hat.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Petr Tesarik <ptesarik@...e.cz>,
        linuxppc-dev <linuxppc-dev@...abs.org>,
        Kexec-ml <kexec@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>
Subject: Re: [RESEND PATCH v5 00/11] ppc64: enable kdump support for
 kexec_file_load syscall



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