Message-ID: <303695cc-d3ea-9f51-1489-07d27d4253d4@oracle.com>
Date:   Mon, 1 Jun 2020 14:30:34 -0500
From:   John Donnelly <John.P.donnelly@...cle.com>
To:     Prabhakar Kushwaha <prabhakar.pkin@...il.com>,
        Chen Zhou <chenzhou10@...wei.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, dyoung@...hat.com,
        bhe@...hat.com, robh+dt@...nel.org, arnd@...db.de,
        devicetree@...r.kernel.org,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        kexec mailing list <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        horms@...ge.net.au, guohanjun@...wei.com,
        Prabhakar Kushwaha <pkushwaha@...vell.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH v8 0/5] support reserving crashkernel above 4G on arm64
 kdump

Hi,


On 6/1/20 7:02 AM, Prabhakar Kushwaha wrote:
> Hi Chen,
>
> On Thu, May 21, 2020 at 3:05 PM Chen Zhou <chenzhou10@...wei.com> 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 [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-May/025128.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbvpn1uM1$
>> [v1]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/2/1174__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbt0xN9PE$
>> [v2]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/86__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbub7yUQH$
>> [v3]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/306__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbnc4zPPV$
>> [v4]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/15/273__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbvsAsZLu$
>> [v5]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/5/6/1360__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbl24n-79$
>> [v6]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/8/30/142__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbs7r8G2a$
>> [v7]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/12/23/411__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbiFUH90G$
>>
>> Chen Zhou (5):
>>    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
>>    dt-bindings: chosen: Document linux,low-memory-range for arm64 kdump
>>
> We are getting "warn_alloc" [1] warning during boot of kdump kernel
> with bootargs as [2] of primary kernel.
> This error observed on ThunderX2  ARM64 platform.
>
> It is observed with latest upstream tag (v5.7-rc3) with this patch set
>   and https://urldefense.com/v3/__https://lists.infradead.org/pipermail/kexec/2020-May/025128.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbiIAAlzu$
> Also **without** this patch-set
> "https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg806882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbjC6ujMA$"
>
> This issue comes whenever crashkernel memory is reserved after 0xc000_0000.
> More details discussed earlier in
> https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg806882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbjC6ujMA$  without any
> solution
>
> This patch-set is expected to solve similar kind of issue.
> i.e. low memory is only targeted for DMA, swiotlb; So above mentioned
> observation should be considered/fixed. .
>
> --pk
>
> [1]
> [   30.366695] DMI: Cavium Inc. Saber/Saber, BIOS
> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy
> [   30.367696] NET: Registered protocol family 16
> [   30.369973] swapper/0: page allocation failure: order:6,
> mode:0x1(GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
> [   30.369980] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc3+ #121
> [   30.369981] Hardware name: Cavium Inc. Saber/Saber, BIOS
> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy
> [   30.369984] Call trace:
> [   30.369989]  dump_backtrace+0x0/0x1f8
> [   30.369991]  show_stack+0x20/0x30
> [   30.369997]  dump_stack+0xc0/0x10c
> [   30.370001]  warn_alloc+0x10c/0x178
> [   30.370004]  __alloc_pages_slowpath.constprop.111+0xb10/0xb50
> [   30.370006]  __alloc_pages_nodemask+0x2b4/0x300
> [   30.370008]  alloc_page_interleave+0x24/0x98
> [   30.370011]  alloc_pages_current+0xe4/0x108
> [   30.370017]  dma_atomic_pool_init+0x44/0x1a4
> [   30.370020]  do_one_initcall+0x54/0x228
> [   30.370027]  kernel_init_freeable+0x228/0x2cc
> [   30.370031]  kernel_init+0x1c/0x110
> [   30.370034]  ret_from_fork+0x10/0x18
> [   30.370036] Mem-Info:
> [   30.370064] active_anon:0 inactive_anon:0 isolated_anon:0
> [   30.370064]  active_file:0 inactive_file:0 isolated_file:0
> [   30.370064]  unevictable:0 dirty:0 writeback:0 unstable:0
> [   30.370064]  slab_reclaimable:34 slab_unreclaimable:4438
> [   30.370064]  mapped:0 shmem:0 pagetables:14 bounce:0
> [   30.370064]  free:1537719 free_pcp:219 free_cma:0
> [   30.370070] Node 0 active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB
> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB
> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB
> unstable:0kB all_unreclaimable? no
> [   30.370073] Node 1 active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB
> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB
> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB
> unstable:0kB all_unreclaimable? no
> [   30.370079] Node 0 DMA free:0kB min:0kB low:0kB high:0kB
> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB
> present:128kB managed:0kB mlocked:0kB kernel_stack:0kB pagetables:0kB
> bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> [   30.370084] lowmem_reserve[]: 0 250 6063 6063
> [   30.370090] Node 0 DMA32 free:256000kB min:408kB low:664kB
> high:920kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB
> present:269700kB managed:256000kB mlocked:0kB kernel_stack:0kB
> pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> [   30.370094] lowmem_reserve[]: 0 0 5813 5813
> [   30.370100] Node 0 Normal free:5894876kB min:9552kB low:15504kB
> high:21456kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB
> present:8388608kB managed:5953112kB mlocked:0kB kernel_stack:21672kB
> pagetables:56kB bounce:0kB free_pcp:876kB local_pcp:176kB free_cma:0kB
> [   30.370104] lowmem_reserve[]: 0 0 0 0
> [   30.370107] Node 0 DMA: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB
> 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB
> [   30.370113] Node 0 DMA32: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB
> 0*256kB 0*512kB 0*1024kB 1*2048kB (M) 62*4096kB (M) = 256000kB
> [   30.370119] Node 0 Normal: 2*4kB (M) 3*8kB (ME) 2*16kB (UE) 3*32kB
> (UM) 1*64kB (U) 2*128kB (M) 2*256kB (ME) 3*512kB (ME) 3*1024kB (ME)
> 3*2048kB (UME) 1436*4096kB (M) = 5893600kB
> [   30.370129] Node 0 hugepages_total=0 hugepages_free=0
> hugepages_surp=0 hugepages_size=1048576kB
> [   30.370130] 0 total pagecache pages
> [   30.370132] 0 pages in swap cache
> [   30.370134] Swap cache stats: add 0, delete 0, find 0/0
> [   30.370135] Free swap  = 0kB
> [   30.370136] Total swap = 0kB
> [   30.370137] 2164609 pages RAM
> [   30.370139] 0 pages HighMem/MovableOnly
> [   30.370140] 612331 pages reserved
> [   30.370141] 0 pages hwpoisoned
> [   30.370143] DMA: failed to allocate 256 KiB pool for atomic
> coherent allocation


During my testing I saw the same error and Chen's  solution corrected it .

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