Re: arm64 crashkernel fails to boot on acpi-only machines due to ACPI regions being no longer mapped as NOMAP

[Dave Young]

kexec@xxxxxxxxxxxxxxxx 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, &reg);
> >>> >> >>
> >>> >> >>         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?

> 
> Regards,
> Bhupesh
> 
> >> Just FYI, on x86, ACPI tables seems to be exposed to crash dump kernel
> >> via a kernel command line parameter, "memmap=".
> >>
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