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Subject: Re: [PATCH v7 0/4] support reserving crashkernel above 4G on arm64
 kdump
To:     <tglx@linutronix.de>, <mingo@redhat.com>,
        <catalin.marinas@arm.com>, <will@kernel.org>,
        <james.morse@arm.com>, <dyoung@redhat.com>, <bhsharma@redhat.com>,
        <john.p.donnelly@oracle.com>, <pkushwaha@marvell.com>
References: <20191223152349.180172-1-chenzhou10@huawei.com>
CC:     <horms@verge.net.au>, <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <kexec@lists.infradead.org>,
        <linux-doc@vger.kernel.org>
From:   Chen Zhou <chenzhou10@huawei.com>
Message-ID: <a57d46bc-881e-3526-91ca-558bf64e2aa8@huawei.com>
Date:   Thu, 26 Mar 2020 11:09:37 +0800
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Hi all,

Friendly ping...

On 2019/12/23 23:23, Chen Zhou wrote:
> This patch series enable reserving crashkernel above 4G in arm64.
> 
> 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. Currently, crashkernel=Y@X can be used to reserve crashkernel above 4G,
> in this case, if swiotlb or DMA buffers are required, crash dump kernel
> will boot failure because there is no low memory available for allocation.
> 
> To solve these issues, introduce crashkernel=X,low to reserve specified
> size low memory.
> Crashkernel=X tries to reserve memory for the crash dump kernel under
> 4G. If crashkernel=Y,low is specified simultaneously, reserve spcified
> size low memory for crash kdump kernel devices firstly and then reserve
> memory above 4G.
> 
> When crashkernel is reserved above 4G in memory, that is, crashkernel=X,low
> is specified simultaneously, kernel should reserve specified size low memory
> for crash dump kernel devices. So there may be two crash kernel regions, one
> is below 4G, the other is above 4G.
> In order to distinct from the high region and make no effect to the use of
> kexec-tools, rename the low region as "Crash kernel (low)", and add DT property
> "linux,low-memory-range" to crash dump kernel's dtb to pass the low region.
> 
> Besides, we need to modify kexec-tools:
> arm64: kdump: add another DT property to crash dump kernel's dtb(see [1])
> 
> The previous changes and discussions can be retrieved from:
> 
> 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]: http://lists.infradead.org/pipermail/kexec/2019-August/023569.html
> [v1]: https://lkml.org/lkml/2019/4/2/1174
> [v2]: https://lkml.org/lkml/2019/4/9/86
> [v3]: https://lkml.org/lkml/2019/4/9/306
> [v4]: https://lkml.org/lkml/2019/4/15/273
> [v5]: https://lkml.org/lkml/2019/5/6/1360
> [v6]: https://lkml.org/lkml/2019/8/30/142
> 
> Chen Zhou (4):
>   x86: kdump: move reserve_crashkernel_low() into crash_core.c
>   arm64: kdump: reserve crashkenel above 4G for crash dump kernel
>   arm64: kdump: add memory for devices by DT property, low-memory-range
>   kdump: update Documentation about crashkernel on arm64
> 
>  Documentation/admin-guide/kdump/kdump.rst       | 13 +++-
>  Documentation/admin-guide/kernel-parameters.txt | 12 +++-
>  arch/arm64/kernel/setup.c                       |  8 ++-
>  arch/arm64/mm/init.c                            | 61 ++++++++++++++++-
>  arch/x86/kernel/setup.c                         | 62 ++----------------
>  include/linux/crash_core.h                      |  3 +
>  include/linux/kexec.h                           |  2 -
>  kernel/crash_core.c                             | 87 +++++++++++++++++++++++++
>  kernel/kexec_core.c                             | 17 -----
>  9 files changed, 183 insertions(+), 82 deletions(-)
>