Re: [PATCH v10 0/5] support reserving crashkernel above 4G on arm64 kdump
From: John Donnelly
Date: Mon Jul 27 2020 - 08:40:08 EST
On 7/3/20 3:38 AM, chenzhou wrote:
Hi Bhupesh,
On 2020/7/3 15:26, Bhupesh Sharma wrote:
Hi Chen,
On Fri, Jul 3, 2020 at 9:24 AM Chen Zhou <chenzhou10@xxxxxxxxxx> 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.
3. commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32") broken
the arm64 kdump. If the memory reserved for crash dump kernel falled in
ZONE_DMA32, the devices in crash dump kernel need to use ZONE_DMA will alloc
fail.
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 and 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 pass the
low region by reusing DT property "linux,usable-memory-range". We made the low
memory region as the last range of "linux,usable-memory-range" to keep
compatibility with existing user-space and older kdump kernels.
Besides, we need to modify kexec-tools:
arm64: support more than one crash kernel regions(see [1])
Another update is document about DT property 'linux,usable-memory-range':
schemas: update 'linux,usable-memory-range' node schema(see [2])
The previous changes and discussions can be retrieved from:
Changes since [v9]
- Patch 1 add Acked-by from Dave.
- Update patch 5 according to Dave's comments.
- Update chosen schema.
Changes since [v8]
- Reuse DT property "linux,usable-memory-range".
Suggested by Rob, reuse DT property "linux,usable-memory-range" to pass the low
memory region.
- Fix kdump broken with ZONE_DMA reintroduced.
- Update chosen schema.
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-June/020737.html__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su4V80IBu$
[2]: https://urldefense.com/v3/__https://github.com/robherring/dt-schema/pull/19__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su3Exu3Pr$
[v1]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/2/1174__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su_RTeG6n$
[v2]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/86__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su3HI0hvE$
[v3]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/306__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su-DmOkg5$
[v4]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/15/273__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-SuykJijY2$
[v5]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/5/6/1360__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su2YHe5UX$
[v6]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/8/30/142__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su9HL5p7k$
[v7]: https://urldefense.com/v3/__https://lkml.org/lkml/2019/12/23/411__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su_mHOJs0$
[v8]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/5/21/213__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su7UYMTZJ$
[v9]: https://urldefense.com/v3/__https://lkml.org/lkml/2020/6/28/73__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Suxcd0E6t$
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
linux,usable-memory-range
arm64: kdump: fix kdump broken with ZONE_DMA reintroduced
kdump: update Documentation about crashkernel on arm64
Documentation/admin-guide/kdump/kdump.rst | 14 ++-
.../admin-guide/kernel-parameters.txt | 17 +++-
arch/arm64/kernel/setup.c | 8 +-
arch/arm64/mm/init.c | 74 ++++++++++++---
arch/x86/kernel/setup.c | 66 ++------------
include/linux/crash_core.h | 3 +
include/linux/kexec.h | 2 -
kernel/crash_core.c | 90 +++++++++++++++++++
kernel/kexec_core.c | 17 ----
9 files changed, 197 insertions(+), 94 deletions(-)
--
2.20.1
Thanks for the v10.
1. Seems this series is still broken on arm64 boards like ampere and
ThunderX2 (marvell) because of the ZONE_DMA32 related OOM seen while
booting kdump kernel.
Here are details about my environment:
- Latest upstream Linus master branch (5.8.0-rc3) + your v10 patches.
- Latest upstream kexec-tools + your v4 patch.
# dmesg | grep -i crash
[ 0.000000] crashkernel reserved: 0x00000000ca000000 -
0x00000000ea000000 (512 MB)
[ 0.000000] Kernel command line:
BOOT_IMAGE=(hd13,gpt2)/vmlinuz-5.8.0-rc3+
root=/dev/mapper/rhel_hpe--apache--cn99xx--09-root ro
rd.lvm.lv=rhel_hpe-apache-cn99xx-09/root
rd.lvm.lv=rhel_hpe-apache-cn99xx-09/swap crashkernel=512M
[ 58.917523] crashkernel=512M
2. Here is the OOM crash seen while booting the kdump kernel:
[ 0.244724] DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
[ 0.251859] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000188
[ 0.260737] Mem abort info:
[ 0.263553] ESR = 0x96000006
[ 0.266632] EC = 0x25: DABT (current EL), IL = 32 bits
[ 0.271994] SET = 0, FnV = 0
[ 0.275074] EA = 0, S1PTW = 0
[ 0.278239] Data abort info:
[ 0.281141] ISV = 0, ISS = 0x00000006
[ 0.285010] CM = 0, WnR = 0
[ 0.288001] [0000000000000188] user address but active_mm is swapper
[ 0.294420] Internal error: Oops: 96000006 [#1] SMP
[ 0.299344] Modules linked in:
[ 0.302424] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc3+ #8
[ 0.308753] Hardware name: HPE Apollo 70 /C01_APACHE_MB
, BIOS L50_5.13_1.11 06/18/2019
[ 0.318599] pstate: 00400009 (nzcv daif +PAN -UAO BTYPE=--)
[ 0.324228] pc : mem_cgroup_get_nr_swap_pages+0x2c/0x60
[ 0.329506] lr : shrink_lruvec+0x404/0x4f8
[ 0.333638] sp : fffffe0012b8f840
[ 0.336979] x29: fffffe0012b8f840 x28: fffffe00116b3000
[ 0.342343] x27: fffffe0012b8fb00 x26: 0000000000000020
[ 0.347707] x25: 0000000000000000 x24: fffffc0069fffe28
[ 0.353070] x23: 0000000000000000 x22: 0000000000000000
[ 0.358433] x21: 000000000000003c x20: fffffe0012b8fa98
[ 0.363796] x19: 0000000000000000 x18: 0000000000000010
[ 0.369159] x17: 00000000bd8afee8 x16: 000000001260aa76
[ 0.374523] x15: ffffffffffffffff x14: fffffe00116b3988
[ 0.379886] x13: fffffe0092b8faa7 x12: fffffe0012b8faaf
[ 0.385248] x11: fffffe00116f1000 x10: fffffe0012b8fa30
[ 0.390612] x9 : fffffe0010244ebc x8 : 0000000000000000
[ 0.395975] x7 : 0000000000000020 x6 : 00000000ffff8ae3
[ 0.401338] x5 : 0000000000000000 x4 : fffffc004da89000
[ 0.406701] x3 : 0000000000000000 x2 : 0000000000000000
[ 0.412064] x1 : fffffe00116bf000 x0 : 0000000000000000
[ 0.417427] Call trace:
[ 0.419891] mem_cgroup_get_nr_swap_pages+0x2c/0x60
[ 0.424815] shrink_node+0x1a8/0x688
[ 0.428420] do_try_to_free_pages+0xe8/0x448
[ 0.432729] try_to_free_pages+0x110/0x230
[ 0.436863] __alloc_pages_slowpath.constprop.106+0x2b8/0xb48
[ 0.442666] __alloc_pages_nodemask+0x2ac/0x2f8
[ 0.447239] alloc_page_interleave+0x20/0x90
[ 0.451548] alloc_pages_current+0xdc/0xf8
[ 0.455681] atomic_pool_expand+0x60/0x210
[ 0.459817] __dma_atomic_pool_init+0x50/0xa4
[ 0.464214] dma_atomic_pool_init+0xac/0x158
[ 0.468522] do_one_initcall+0x50/0x218
[ 0.472393] kernel_init_freeable+0x22c/0x2d0
[ 0.476792] kernel_init+0x18/0x110
[ 0.480310] ret_from_fork+0x10/0x18
[ 0.483918] Code: 350001e3 d503201f f9450024 1400000a (f940c401)
[ 0.490074] ---[ end trace e5a9147af159e580 ]---
[ 0.494734] Kernel panic - not syncing: Fatal exception
[ 0.500010] Rebooting in 10 seconds..
3. Did you test your patch with a simple crashkernel=512M command line
(without using the crashkernel hi/lo or crashkernel=X@Y format)?
Anyway, since this implementation still needs rework, we can go ahead
with the arrangement of limiting the crashkernel allocation in
ZONE_DMA range (as I suggested in another patch series
<https://urldefense.com/v3/__http://lists.infradead.org/pipermail/kexec/2020-July/020777.html__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su56QERe_$ >) in
the meanwhile. to ensure the upstream kernel can still support kdump
on arm64 boards where it was working before the ZONE_DMA32 changes
were introduced for arm64.
Please let me know your views,
Thanks for your test and sharing your views. I have no questions about the 1 and 2 you mentioned.
I charity the issue in my patch 4 and suggest to use the parameter like
"crashkernel=X crashkernel=Y,low" if CONFIG_ZONE_DMA is enabled.
I also document this in doc in patch 5.
I choose to address the issue based on the "reserving crashkernel above 4G",
because we just need to adjust the low memory limit instead of limiting the
whole crahshkernel to ZONE_DMA.
details: https://urldefense.com/v3/__https://lkml.org/lkml/2020/7/3/64__;!!GqivPVa7Brio!LQeROomdhNOjTVFcQP6pLxDm9nhbEsY3vqZMI7NHeDU_VnCaN7iw2DJ84x-Su1vtGdek$
But you are right, arm64 kdump is broken for long time, including the issue you addressed
"Append new variables to vmcoreinfo (TCR_EL1.T1SZ for arm64 and MAX_PHYSMEM_BITS for all archs)".
I agree with you to make it work as soon as possible.
Ping James, Will,
any other comments about this patch series?
Thanks,
Chen Zhou
Hi James and Will,
 This patch set has been in review for over a year, since May of 2019.
 What is holding up getting this accepted ?