On Tue, Dec 19, 2017 at 02:58:20AM +0530, Bhupesh Sharma wrote: > Hi Dave, > > On Mon, Dec 18, 2017 at 10:46 AM, Dave Young <dyoung@xxxxxxxxxx> wrote: > > kexec@fedoraproject... is for Fedora kexec scripts discussion, changed it > > to kexec@xxxxxxxxxxxxxxxxxxx > > > > 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@xxxxxxxxxx> wrote: > >> > On 15 December 2017 at 09:59, AKASHI Takahiro > >> > <takahiro.akashi@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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); This macro can be defined in two ways depending on ACPI_MISALIGNMENT_NOT_SUPPORTED in drivers/acpi/acpica/acmarcos.h. So, in principle, any use of ioremap() in acpi_os_ioremap() may be in conflict with those definitions here. This suggests that, under the current code base, we must expose ACPI reclaim regions as memblocks (i.e. via usable-memory-range) in order to avoid the reported issue. Thanks, -Takahiro AKASHI > 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@xxxxxxxxxxxxxxxxxxxxxxx > >> To unsubscribe send an email to kexec-leave@xxxxxxxxxxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
