Re: [PATCH v8 0/5] support reserving crashkernel above 4G on arm64 kdump
From: John Donnelly <hidden>
Date: 2020-06-02 14:42:54
Also in:
kexec, linux-devicetree, linux-doc, lkml
On Jun 2, 2020, at 12:38 AM, Prabhakar Kushwaha [off-list ref] wrote: On Tue, Jun 2, 2020 at 3:29 AM John Donnelly [off-list ref] wrote:quoted
Hi . See below !quoted
On Jun 1, 2020, at 4:02 PM, Bhupesh Sharma [off-list ref] wrote: Hi John, On Tue, Jun 2, 2020 at 1:01 AM John Donnelly [off-list ref] wrote:quoted
Hi, On 6/1/20 7:02 AM, Prabhakar Kushwaha wrote:quoted
Hi Chen, On Thu, May 21, 2020 at 3:05 PM Chen Zhou [off-list ref] wrote:quoted
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 kdumpWe 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 allocationDuring my testing I saw the same error and Chen's solution corrected it .Which combination you are using on your side? I am using Prabhakar's suggested environment and can reproduce the issue with or without Chen's crashkernel support above 4G patchset. I am also using a ThunderX2 platform with latest makedumpfile code and kexec-tools (with the suggested patch <https://urldefense.com/v3/__https://lists.infradead.org/pipermail/kexec/2020-May/025128.html__;!!GqivPVa7Brio!J6lUig58-Gw6TKZnEEYzEeSU36T-1SqlB1kImU00xtX_lss5Tx-JbUmLE9TJC3foXBLg$ >). Thanks, BhupeshI did this activity 5 months ago and I have moved on to other activities. My DMA failures were related to PCI devices that could not be enumerated because low-DMA space was not available when crashkernel was moved above 4G; I don’t recall the exact platform. For this failure ,quoted
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DMA: failed to allocate 256 KiB pool for atomic coherent allocationIs due to : 3618082c ("arm64 use both ZONE_DMA and ZONE_DMA32") With the introduction of ZONE_DMA to support the Raspberry DMA region below 1G, the crashkernel is placed in the upper 4G ZONE_DMA_32 region. Since the crashkernel does not have access to the ZONE_DMA region, it prints out call trace during bootup. It is due to having this CONFIG item ON : CONFIG_ZONE_DMA=y Turning off ZONE_DMA fixes a issue and Raspberry PI 4 will use the device tree to specify memory below 1G.Disabling ZONE_DMA is temporary solution. We may need proper solution
Perhaps the Raspberry platform configuration dependencies need separated from “server class” Arm equipment ? Or auto-configured on boot ? Consult an expert ;-)
quoted hunk ↗ jump to hunk
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I would like to see Chen’s feature added , perhaps as EXPERIMENTAL, so we can get some configuration testing done on it. It corrects having a DMA zone in low memory while crash-kernel is above 4GB. This has been going on for a year now.I will also like this patch to be added in Linux as early as possible. Issue mentioned by me happens with or without this patch. This patch-set can consider fixing because it uses low memory for DMA & swiotlb only. We can consider restricting crashkernel within the required range like belowdiff --git a/kernel/crash_core.c b/kernel/crash_core.c index 7f9e5a6dc48c..bd67b90d35bd 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c@@ -354,7 +354,7 @@ int __init reserve_crashkernel_low(void) return 0; } - low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN); + low_base = memblock_find_in_range(0,0xc0000000, low_size, CRASH_ALIGN); if (!low_base) { pr_err("Cannot reserve %ldMB crashkernel low memory,please try smaller size.\n", (unsigned long)(low_size >> 20));
I suspect 0xc0000000 would need to be a CONFIG item and not hard-coded.
Similar change can be considered for scenario "without" this patch. But it will decrease memory availability for crashkernel. Hence increase the failure probability of crashkernel reservation. --pk
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