On Mon, Dec 18, 2017 at 01:16:57PM +0800, Dave Young wrote: > kexec@fedoraproject... is for Fedora kexec scripts discussion, changed it > to kexec@xxxxxxxxxxxxxxxxxxx > > Also add linux-acpi list Thank you. > 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. It is natural if that region is out of memblocks. > > 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 this (ESR = 0x96000021) means that Data Abort and Alignment fault happened. As ioremap() makes the mapping as "Device memory", unaligned memory access won't be allowed. > > [ 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? So should we always avoid ioremap() in acpi_os_ioremap() entirely, or modify acpi_ns_lookup() (or any acpi functions') to prevent unaligned accesses? (I didn't find out how unaligned accesses could happen there.) Thanks, -Takahiro AKASHI > > > > 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-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
