On 2020/2/24 23:25, John Donnelly wrote: > > >> On Jan 16, 2020, at 9:47 AM, John Donnelly <john.p.donnelly@xxxxxxxxxx> wrote: >> >> >> >>> On Jan 16, 2020, at 9:17 AM, James Morse <james.morse@xxxxxxx> wrote: >>> >>> Hi guys, >>> >>> On 28/12/2019 09:32, Dave Young wrote: >>>> On 12/27/19 at 07:04pm, Chen Zhou wrote: >>>>> On 2019/12/27 13:54, Dave Young wrote: >>>>>> On 12/23/19 at 11:23pm, Chen Zhou wrote: >>>>>>> In preparation for supporting reserve_crashkernel_low in arm64 as >>>>>>> x86_64 does, move reserve_crashkernel_low() into kernel/crash_core.c. >>>>>>> >>>>>>> Note, in arm64, we reserve low memory if and only if crashkernel=X,low >>>>>>> is specified. Different with x86_64, don't set low memory automatically. >>>>>> >>>>>> Do you have any reason for the difference? I'd expect we have same >>>>>> logic if possible and remove some of the ifdefs. >>>>> >>>>> In x86_64, if we reserve crashkernel above 4G, then we call reserve_crashkernel_low() >>>>> to reserve low memory. >>>>> >>>>> In arm64, to simplify, we call reserve_crashkernel_low() at the beginning of reserve_crashkernel() >>>>> and then relax the arm64_dma32_phys_limit if reserve_crashkernel_low() allocated something. >>>>> In this case, if reserve crashkernel below 4G there will be 256M low memory set automatically >>>>> and this needs extra considerations. >>> >>>> Sorry that I did not read the old thread details and thought that is >>>> arch dependent. But rethink about that, it would be better that we can >>>> have same semantic about crashkernel parameters across arches. If we >>>> make them different then it causes confusion, especially for >>>> distributions. >>> >>> Surely distros also want one crashkernel* string they can use on all platforms without >>> having to detect the kernel version, platform or changeable memory layout... >>> >>> >>>> OTOH, I thought if we reserve high memory then the low memory should be >>>> needed. There might be some exceptions, but I do not know the exact >>>> one, >>> >>>> can we make the behavior same, and special case those systems which >>>> do not need low memory reservation. >>> >>> Its tricky to work out which systems are the 'normal' ones. >>> >>> We don't have a fixed memory layout for arm64. Some systems have no memory below 4G. >>> Others have no memory above 4G. >>> >>> Chen Zhou's machine has some memory below 4G, but its too precious to reserve a large >>> chunk for kdump. Without any memory below 4G some of the drivers won't work. >>> >>> I don't see what distros can set as their default for all platforms if high/low are >>> mutually exclusive with the 'crashkernel=' in use today. How did x86 navigate this, ... or >>> was it so long ago? >>> >>> No one else has reported a problem with the existing placement logic, hence treating this >>> 'low' thing as the 'in addition' special case. >> >> >> Hi, >> >> I am seeing similar Arm crash dump issues on 5.4 kernels where we need rather large amount of crashkernel memory reserved that is not available below 4GB ( The maximum reserved size appears to be around 768M ) . When I pick memory range higher than 4GB , I see adapters that fail to initialize : >> >> >> There is no low-memory <4G memory for DMA ; >> >> [ 11.506792] kworker/0:14: page allocation failure: order:0, >> mode:0x104(GFP_DMA32|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0 >> [ 11.518793] CPU: 0 PID: 150 Comm: kworker/0:14 Not tainted >> 5.4.0-1948.3.el8uek.aarch64 #1 >> [ 11.526955] Hardware name: To be filled by O.E.M. Saber/Saber, BIOS >> 0ACKL025 01/18/2019 >> [ 11.534948] Workqueue: events work_for_cpu_fn >> [ 11.539291] Call trace: >> [ 11.541727] dump_backtrace+0x0/0x18c >> [ 11.545376] show_stack+0x24/0x30 >> [ 11.548679] dump_stack+0xbc/0xe0 >> [ 11.551982] warn_alloc+0xf0/0x15c >> [ 11.555370] __alloc_pages_slowpath+0xb4c/0xb84 >> [ 11.559887] __alloc_pages_nodemask+0x2d0/0x330 >> [ 11.564405] alloc_pages_current+0x8c/0xf8 >> [ 11.568496] ttm_bo_device_init+0x188/0x220 [ttm] >> [ 11.573187] drm_vram_mm_init+0x58/0x80 [drm_vram_helper] >> [ 11.578572] drm_vram_helper_alloc_mm+0x64/0xb0 [drm_vram_helper] >> [ 11.584655] ast_mm_init+0x38/0x80 [ast] >> [ 11.588566] ast_driver_load+0x474/0xa70 [ast] >> [ 11.593029] drm_dev_register+0x144/0x1c8 [drm] >> [ 11.597573] drm_get_pci_dev+0xa4/0x168 [drm] >> [ 11.601919] ast_pci_probe+0x8c/0x9c [ast] >> [ 11.606004] local_pci_probe+0x44/0x98 >> [ 11.609739] work_for_cpu_fn+0x20/0x30 >> [ 11.613474] process_one_work+0x1c4/0x41c >> [ 11.617470] worker_thread+0x150/0x4b0 >> [ 11.621206] kthread+0x110/0x114 >> [ 11.624422] ret_from_fork+0x10/0x18 >> >> This failure is related to a graphics adapter. >> >> The more complex kdump configurations that use networking stack to NFS mount a filesystem to dump to , or use ssh to copy to another machine, require more crashkernel memory reservations than perhaps the “default*” settings of a minimal kdump that creates a minimal vmcore to local storage in /var/crash. If crashkernel is too small I get Out of Memory issues and the entire vmcore process fails. >> >> ( *default kdump setting I assume are a minimal vmcore to /var/crash using primary boot device where /root is located ) >> > Hi Chen, > > > I was able to unit test these series of kernel patches applied to a 5.4.17 test kernel along with the kexec CLI change : > > 0001-arm64-kdump-add-another-DT-property-to-crash-dump-ke.patch > > Applied to : > > kexec-tools-2.0.19-12.0.4.el8.src.rpm > > And obtained a vmcore using this cmdline : > > BOOT_IMAGE=(hd6,gpt2)/vmlinuz-5.4.17-4-uek6m_ol8-jpdonnel+ root=/dev/mapper/ol01-root ro crashkernel=2048M@35G crashkernel=250M,low rd.lvm.lv=ol01/root rd.lvm.lv=ol01/swap console=ttyS4 loglevel=7 > > Can you add : > > Tested-by: John Donnelly <John.p.donnelly@xxxxxxxxxx> > > > How can we get these changes included into an rc kernel release ? > > Thanks, > > John. Hi all, Friendly ping... > > >> >> >> >>> >>> >>>>> previous discusses: >>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_6_5_670&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=jOAu1DTDpohsWszalfTCYx46eGF19TSWVLchN5yBPgk&s=gS9BLOkmj78lP5L7SP6_VLHwvP249uWKaE2R7N7sxgM&e= >>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_6_13_229&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=jOAu1DTDpohsWszalfTCYx46eGF19TSWVLchN5yBPgk&s=U1Nis29n3A7XSBzED53fiE4MDAv5NlxYp1UorvvBOOw&e= >>>> >>>> Another concern from James: >>>> " >>>> With both crashk_low_res and crashk_res, we end up with two entries in /proc/iomem called >>>> "Crash kernel". Because its sorted by address, and kexec-tools stops searching when it >>>> find "Crash kernel", you are always going to get the kernel placed in the lower portion. >>>> " >>>> >>>> The kexec-tools code is iterating all "Crash kernel" ranges and add them >>>> in an array. In X86 code, it uses the higher range to locate memory. >>> >>> Then my hurried reading of what the user-space code does was wrong! >>> >>> If kexec-tools places the kernel in the low region, there may not be enough memory left >>> for whatever purpose it was reserved for. This was the motivation for giving it a >>> different name. >>> >>> >>> Thanks, >>> >>> James >>> >>> _______________________________________________ >>> kexec mailing list >>> kexec@xxxxxxxxxxxxxxxxxxx >>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_kexec&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=jOAu1DTDpohsWszalfTCYx46eGF19TSWVLchN5yBPgk&s=bqp02iQDP_Ez-XvLIvj-IPHqbbZwMPlDgmEcG8vhXFE&e= >> >> >> _______________________________________________ >> kexec mailing list >> kexec@xxxxxxxxxxxxxxxxxxx >> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_kexec&d=DwIGaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=whm9_BOrgAjJvBn0Ey_brHhFg2YMU_P0HF02dhgdgwU&s=vLar_m5JbicYwwuo6N84ZiBDGZUPM8bBLSPLQBtPZNY&e= > > > . >
