Hi Dave, On Mon, Dec 18, 2017 at 10:46 AM, Dave Young <dyoung at redhat.com> wrote: > kexec at fedoraproject... is for Fedora kexec scripts discussion, changed it > to kexec at lists.infradead.org > > Also add linux-acpi list > On 12/18/17 at 02:31am, Bhupesh Sharma wrote: >> On Fri, Dec 15, 2017 at 3:05 PM, Ard Biesheuvel >> <ard.biesheuvel at linaro.org> wrote: >> > On 15 December 2017 at 09:59, AKASHI Takahiro >> > <takahiro.akashi at linaro.org> wrote: >> >> On Wed, Dec 13, 2017 at 12:17:22PM +0000, Ard Biesheuvel wrote: >> >>> On 13 December 2017 at 12:16, AKASHI Takahiro >> >>> <takahiro.akashi at linaro.org> wrote: >> >>> > On Wed, Dec 13, 2017 at 10:49:27AM +0000, Ard Biesheuvel wrote: >> >>> >> On 13 December 2017 at 10:26, AKASHI Takahiro >> >>> >> <takahiro.akashi at linaro.org> wrote: >> >>> >> > Bhupesh, Ard, >> >>> >> > >> >>> >> > On Wed, Dec 13, 2017 at 03:21:59AM +0530, Bhupesh Sharma wrote: >> >>> >> >> Hi Ard, Akashi >> >>> >> >> >> >>> >> > (snip) >> >>> >> > >> >>> >> >> Looking deeper into the issue, since the arm64 kexec-tools uses the >> >>> >> >> 'linux,usable-memory-range' dt property to allow crash dump kernel to >> >>> >> >> identify its own usable memory and exclude, at its boot time, any >> >>> >> >> other memory areas that are part of the panicked kernel's memory. >> >>> >> >> (see https://www.kernel.org/doc/Documentation/devicetree/bindings/chosen.txt >> >>> >> >> , for details) >> >>> >> > >> >>> >> > Right. >> >>> >> > >> >>> >> >> 1). Now when 'kexec -p' is executed, this node is patched up only >> >>> >> >> with the crashkernel memory range: >> >>> >> >> >> >>> >> >> /* add linux,usable-memory-range */ >> >>> >> >> nodeoffset = fdt_path_offset(new_buf, "/chosen"); >> >>> >> >> result = fdt_setprop_range(new_buf, nodeoffset, >> >>> >> >> PROP_USABLE_MEM_RANGE, &crash_reserved_mem, >> >>> >> >> address_cells, size_cells); >> >>> >> >> >> >>> >> >> (see https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/tree/kexec/arch/arm64/kexec-arm64.c#n465 >> >>> >> >> , for details) >> >>> >> >> >> >>> >> >> 2). This excludes the ACPI reclaim regions irrespective of whether >> >>> >> >> they are marked as System RAM or as RESERVED. As, >> >>> >> >> 'linux,usable-memory-range' dt node is patched up only with >> >>> >> >> 'crash_reserved_mem' and not 'system_memory_ranges' >> >>> >> >> >> >>> >> >> 3). As a result when the crashkernel boots up it doesn't find this >> >>> >> >> ACPI memory and crashes while trying to access the same: >> >>> >> >> >> >>> >> >> # kexec -p /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname >> >>> >> >> -r`.img --reuse-cmdline -d >> >>> >> >> >> >>> >> >> [snip..] >> >>> >> >> >> >>> >> >> Reserved memory range >> >>> >> >> 000000000e800000-000000002e7fffff (0) >> >>> >> >> >> >>> >> >> Coredump memory ranges >> >>> >> >> 0000000000000000-000000000e7fffff (0) >> >>> >> >> 000000002e800000-000000003961ffff (0) >> >>> >> >> 0000000039d40000-000000003ed2ffff (0) >> >>> >> >> 000000003ed60000-000000003fbfffff (0) >> >>> >> >> 0000001040000000-0000001ffbffffff (0) >> >>> >> >> 0000002000000000-0000002ffbffffff (0) >> >>> >> >> 0000009000000000-0000009ffbffffff (0) >> >>> >> >> 000000a000000000-000000affbffffff (0) >> >>> >> >> >> >>> >> >> 4). So if we revert Ard's patch or just comment the fixing up of the >> >>> >> >> memory cap'ing passed to the crash kernel inside >> >>> >> >> 'arch/arm64/mm/init.c' (see below): >> >>> >> >> >> >>> >> >> static void __init fdt_enforce_memory_region(void) >> >>> >> >> { >> >>> >> >> struct memblock_region reg = { >> >>> >> >> .size = 0, >> >>> >> >> }; >> >>> >> >> >> >>> >> >> of_scan_flat_dt(early_init_dt_scan_usablemem, ®); >> >>> >> >> >> >>> >> >> if (reg.size) >> >>> >> >> //memblock_cap_memory_range(reg.base, reg.size); /* >> >>> >> >> comment this out */ >> >>> >> >> } >> >>> >> > >> >>> >> > Please just don't do that. It can cause a fatal damage on >> >>> >> > memory contents of the *crashed* kernel. >> >>> >> > >> >>> >> >> 5). Both the above temporary solutions fix the problem. >> >>> >> >> >> >>> >> >> 6). However exposing all System RAM regions to the crashkernel is not >> >>> >> >> advisable and may cause the crashkernel or some crashkernel drivers to >> >>> >> >> fail. >> >>> >> >> >> >>> >> >> 6a). I am trying an approach now, where the ACPI reclaim regions are >> >>> >> >> added to '/proc/iomem' separately as ACPI reclaim regions by the >> >>> >> >> kernel code and on the other hand the user-space 'kexec-tools' will >> >>> >> >> pick up the ACPI reclaim regions from '/proc/iomem' and add it to the >> >>> >> >> dt node 'linux,usable-memory-range' >> >>> >> > >> >>> >> > I still don't understand why we need to carry over the information >> >>> >> > about "ACPI Reclaim memory" to crash dump kernel. In my understandings, >> >>> >> > such regions are free to be reused by the kernel after some point of >> >>> >> > initialization. Why does crash dump kernel need to know about them? >> >>> >> > >> >>> >> >> >>> >> Not really. According to the UEFI spec, they can be reclaimed after >> >>> >> the OS has initialized, i.e., when it has consumed the ACPI tables and >> >>> >> no longer needs them. Of course, in order to be able to boot a kexec >> >>> >> kernel, those regions needs to be preserved, which is why they are >> >>> >> memblock_reserve()'d now. >> >>> > >> >>> > For my better understandings, who is actually accessing such regions >> >>> > during boot time, uefi itself or efistub? >> >>> > >> >>> >> >>> No, only the kernel. This is where the ACPI tables are stored. For >> >>> instance, on QEMU we have >> >>> >> >>> ACPI: RSDP 0x0000000078980000 000024 (v02 BOCHS ) >> >>> ACPI: XSDT 0x0000000078970000 000054 (v01 BOCHS BXPCFACP 00000001 >> >>> 01000013) >> >>> ACPI: FACP 0x0000000078930000 00010C (v05 BOCHS BXPCFACP 00000001 >> >>> BXPC 00000001) >> >>> ACPI: DSDT 0x0000000078940000 0011DA (v02 BOCHS BXPCDSDT 00000001 >> >>> BXPC 00000001) >> >>> ACPI: APIC 0x0000000078920000 000140 (v03 BOCHS BXPCAPIC 00000001 >> >>> BXPC 00000001) >> >>> ACPI: GTDT 0x0000000078910000 000060 (v02 BOCHS BXPCGTDT 00000001 >> >>> BXPC 00000001) >> >>> ACPI: MCFG 0x0000000078900000 00003C (v01 BOCHS BXPCMCFG 00000001 >> >>> BXPC 00000001) >> >>> ACPI: SPCR 0x00000000788F0000 000050 (v02 BOCHS BXPCSPCR 00000001 >> >>> BXPC 00000001) >> >>> ACPI: IORT 0x00000000788E0000 00007C (v00 BOCHS BXPCIORT 00000001 >> >>> BXPC 00000001) >> >>> >> >>> covered by >> >>> >> >>> efi: 0x0000788e0000-0x00007894ffff [ACPI Reclaim Memory ...] >> >>> ... >> >>> efi: 0x000078970000-0x00007898ffff [ACPI Reclaim Memory ...] >> >> >> >> OK. I mistakenly understood those regions could be freed after exiting >> >> UEFI boot services. >> >> >> >>> >> >>> >> So it seems that kexec does not honour the memblock_reserve() table >> >>> >> when booting the next kernel. >> >>> > >> >>> > not really. >> >>> > >> >>> >> > (In other words, can or should we skip some part of ACPI-related init code >> >>> >> > on crash dump kernel?) >> >>> >> > >> >>> >> >> >>> >> I don't think so. And the change to the handling of ACPI reclaim >> >>> >> regions only revealed the bug, not created it (given that other >> >>> >> memblock_reserve regions may be affected as well) >> >>> > >> >>> > As whether we should honor such reserved regions over kexec'ing >> >>> > depends on each one's specific nature, we will have to take care one-by-one. >> >>> > As a matter of fact, no information about "reserved" memblocks is >> >>> > exposed to user space (via proc/iomem). >> >>> > >> >>> >> >>> That is why I suggested (somewhere in this thread?) to not expose them >> >>> as 'System RAM'. Do you think that could solve this? >> >> >> >> Memblock-reserv'ing them is necessary to prevent their corruption and >> >> marking them under another name in /proc/iomem would also be good in order >> >> not to allocate them as part of crash kernel's memory. >> >> >> > >> > I agree. However, this may not be entirely trivial, since iterating >> > over the memblock_reserved table and creating iomem entries may result >> > in collisions. >> >> I found a method (using the patch I shared earlier in this thread) to mark these >> entries as 'ACPI reclaim memory' ranges rather than System RAM or >> reserved regions. >> >> >> But I'm not still convinced that we should export them in useable- >> >> memory-range to crash dump kernel. They will be accessed through >> >> acpi_os_map_memory() and so won't be required to be part of system ram >> >> (or memblocks), I guess. >> > >> > Agreed. They will be covered by the linear mapping in the boot kernel, >> > and be mapped explicitly via ioremap_cache() in the kexec kernel, >> > which is exactly what we want in this case. >> >> Now this is what is confusing me. I don't see the above happening. >> >> I see that the primary kernel boots up and adds the ACPI regions via: >> acpi_os_ioremap >> -> ioremap_cache >> >> But during the crashkernel boot, ''acpi_os_ioremap' calls >> 'ioremap' for the ACPI Reclaim Memory regions and not the _cache >> variant. >> >> And it fails while accessing the ACPI tables: >> >> [ 0.039205] ACPI: Core revision 20170728 >> pud=000000002e7d0003, *pmd=000000002e7c0003, *pte=00e8000039710707 >> [ 0.095098] Internal error: Oops: 96000021 [#1] SMP >> [ 0.100022] Modules linked in: >> [ 0.103102] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc6 #1 >> [ 0.109432] task: ffff000008d05180 task.stack: ffff000008cc0000 >> [ 0.115414] PC is at acpi_ns_lookup+0x25c/0x3c0 >> [ 0.119987] LR is at acpi_ds_load1_begin_op+0xa4/0x294 >> [ 0.125175] pc : [<ffff0000084a6764>] lr : [<ffff00000849b4f8>] >> pstate: 60000045 >> [ 0.132647] sp : ffff000008ccfb40 >> [ 0.135989] x29: ffff000008ccfb40 x28: ffff000008a9f2a4 >> [ 0.141354] x27: ffff0000088be820 x26: 0000000000000000 >> [ 0.146718] x25: 000000000000001b x24: 0000000000000001 >> [ 0.152083] x23: 0000000000000001 x22: ffff000009710027 >> [ 0.157447] x21: ffff000008ccfc50 x20: 0000000000000001 >> [ 0.162812] x19: 000000000000001b x18: 0000000000000005 >> [ 0.168176] x17: 0000000000000000 x16: 0000000000000000 >> [ 0.173541] x15: 0000000000000000 x14: 000000000000038e >> [ 0.178905] x13: ffffffff00000000 x12: ffffffffffffffff >> [ 0.184270] x11: 0000000000000006 x10: 00000000ffffff76 >> [ 0.189634] x9 : 000000000000005f x8 : ffff8000126d0140 >> [ 0.194998] x7 : 0000000000000000 x6 : ffff000008ccfc50 >> [ 0.200362] x5 : ffff80000fe62c00 x4 : 0000000000000001 >> [ 0.205727] x3 : ffff000008ccfbe0 x2 : ffff0000095e3980 >> [ 0.211091] x1 : ffff000009710027 x0 : 0000000000000000 >> [ 0.216456] Process swapper/0 (pid: 0, stack limit = 0xffff000008cc0000) >> [ 0.223224] Call trace: >> [ 0.225688] Exception stack(0xffff000008ccfa00 to 0xffff000008ccfb40) >> [ 0.232194] fa00: 0000000000000000 ffff000009710027 >> ffff0000095e3980 ffff000008ccfbe0 >> [ 0.240106] fa20: 0000000000000001 ffff80000fe62c00 >> ffff000008ccfc50 0000000000000000 >> [ 0.248018] fa40: ffff8000126d0140 000000000000005f >> 00000000ffffff76 0000000000000006 >> [ 0.255931] fa60: ffffffffffffffff ffffffff00000000 >> 000000000000038e 0000000000000000 >> [ 0.263843] fa80: 0000000000000000 0000000000000000 >> 0000000000000005 000000000000001b >> [ 0.271754] faa0: 0000000000000001 ffff000008ccfc50 >> ffff000009710027 0000000000000001 >> [ 0.279667] fac0: 0000000000000001 000000000000001b >> 0000000000000000 ffff0000088be820 >> [ 0.287579] fae0: ffff000008a9f2a4 ffff000008ccfb40 >> ffff00000849b4f8 ffff000008ccfb40 >> [ 0.295491] fb00: ffff0000084a6764 0000000060000045 >> ffff000008ccfb40 ffff000008260a18 >> [ 0.303403] fb20: ffffffffffffffff ffff0000087f3fb0 >> ffff000008ccfb40 ffff0000084a6764 >> [ 0.311316] [<ffff0000084a6764>] acpi_ns_lookup+0x25c/0x3c0 >> [ 0.316943] [<ffff00000849b4f8>] acpi_ds_load1_begin_op+0xa4/0x294 >> [ 0.323186] [<ffff0000084ad4ac>] acpi_ps_build_named_op+0xc4/0x198 >> [ 0.329428] [<ffff0000084ad6cc>] acpi_ps_create_op+0x14c/0x270 >> [ 0.335319] [<ffff0000084acfa8>] acpi_ps_parse_loop+0x188/0x5c8 >> [ 0.341298] [<ffff0000084ae048>] acpi_ps_parse_aml+0xb0/0x2b8 >> [ 0.347101] [<ffff0000084a8e10>] acpi_ns_one_complete_parse+0x144/0x184 >> [ 0.353783] [<ffff0000084a8e98>] acpi_ns_parse_table+0x48/0x68 >> [ 0.359675] [<ffff0000084a82cc>] acpi_ns_load_table+0x4c/0xdc >> [ 0.365479] [<ffff0000084b32f8>] acpi_tb_load_namespace+0xe4/0x264 >> [ 0.371723] [<ffff000008baf9b4>] acpi_load_tables+0x48/0xc0 >> [ 0.377350] [<ffff000008badc20>] acpi_early_init+0x9c/0xd0 >> [ 0.382891] [<ffff000008b70d50>] start_kernel+0x3b4/0x43c >> [ 0.388343] Code: b9008fb9 2a000318 36380054 32190318 (b94002c0) >> [ 0.394500] ---[ end trace c46ed37f9651c58e ]--- >> [ 0.399160] Kernel panic - not syncing: Fatal exception >> [ 0.404437] Rebooting in 10 seconds. >> >> So, I think the linear mapping done by the primary kernel does not >> make these accessible in the crash kernel directly. >> >> Any pointers? > > Can you get the code line number for acpi_ns_lookup+0x25c? gdb points to the following code line number: (gdb) list *(acpi_ns_lookup+0x25c) 0xffff0000084aa250 is in acpi_ns_lookup (drivers/acpi/acpica/nsaccess.c:577). 572 } 573 } 574 575 /* Extract one ACPI name from the front of the pathname */ 576 577 ACPI_MOVE_32_TO_32(&simple_name, path); 578 579 /* Try to find the single (4 character) ACPI name */ 580 581 status = (gdb) i.e. ACPI_MOVE_32_TO_32(&simple_name, path); addr2line also confirms the same: # addr2line -e vmlinux ffff0000084aa250 /root/git/kernel-alt/drivers/acpi/acpica/nsaccess.c:577 Regards, Bhupesh >> >> Regards, >> Bhupesh >> >> >> Just FYI, on x86, ACPI tables seems to be exposed to crash dump kernel >> >> via a kernel command line parameter, "memmap=". >> >> >> _______________________________________________ >> kexec mailing list -- kexec at lists.fedoraproject.org >> To unsubscribe send an email to kexec-leave at lists.fedoraproject.org
