Hello Akashi, On Thu, Dec 21, 2017 at 4:04 PM, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote: > Bhupesh, > > Can you test the patch attached below, please? > > It is intended to retain already-reserved regions (ACPI reclaim memory > in this case) in system ram (i.e. memblock.memory) without explicitly > exporting them via usable-memory-range. > (I still have to figure out what the side-effect of this patch is.) > > Thanks, > -Takahiro AKASHI > > On Thu, Dec 21, 2017 at 01:30:43AM +0530, Bhupesh Sharma wrote: >> On Tue, Dec 19, 2017 at 6:39 PM, Ard Biesheuvel >> <ard.biesheuvel at linaro.org> wrote: >> > On 19 December 2017 at 07:09, AKASHI Takahiro >> > <takahiro.akashi at linaro.org> wrote: >> >> On Mon, Dec 18, 2017 at 01:40:09PM +0800, Dave Young wrote: >> >>> On 12/15/17 at 05:59pm, AKASHI Takahiro 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. >> >>> > >> >>> > 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. >> >>> > -> Bhupesh? >> >>> >> >>> I forgot how arm64 kernel retrieve the memory ranges and initialize >> >>> them. If no "e820" like interfaces shouldn't kernel reinitialize all >> >>> the memory according to the efi memmap? For kdump kernel anything other >> >>> than usable memory (which is from the dt node instead) should be >> >>> reinitialized according to efi passed info, no? >> >> >> >> All the regions exported in efi memmap will be added to memblock.memory >> >> in (u)efi_init() and then trimmed down to the exact range specified as >> >> usable-memory-range by fdt_enforce_memory_region(). >> >> >> >> Now I noticed that the current fdt_enforce_memory_region() may not work well >> >> with multiple entries in usable-memory-range. >> >> >> > >> > In any case, the root of the problem is that memory regions lose their >> > 'memory' annotation due to the way the memory map is mangled before >> > being supplied to the kexec kernel. >> > >> > Would it be possible to classify all memory that we want to hide from >> > the kexec kernel as NOMAP instead? That way, it will not be mapped >> > implicitly, but will still be mapped cacheable by acpi_os_ioremap(), >> > so this seems to be the most appropriate way to deal with the host >> > kernel's memory contents. >> >> Hmm. wouldn't appending the acpi reclaim regions to >> 'linux,usable-memory-range' in the dtb being passed to the crashkernel >> be better? Because its indirectly achieving a similar objective >> (although may be a subset of all System RAM regions on the primary >> kernel's memory). >> >> I am not aware of the background about the current kexec-tools >> implementation where we add only the crashkernel range to the dtb >> being passed to the crashkernel. >> >> Probably Akashi can answer better, as to how we arrived at this design >> approach and why we didn't want to expose all System RAM regions (i.e. >> ! NOMPAP regions) to the crashkernel. >> >> I am suspecting that some issues were seen/meet when the System RAM (! >> NOMAP regions) were exposed to the crashkernel, and that's why we >> finalized on this design approach, but this is something which is just >> my guess. >> >> Regards, >> Bhupesh >> >> >>> > >> >>> > Just FYI, on x86, ACPI tables seems to be exposed to crash dump kernel >> >>> > via a kernel command line parameter, "memmap=". >> >>> >> >>> memmap= is only used in old kexec-tools, now we are passing them via >> >>> e820 table. >> >> >> >> Thanks. I remember that you have explained it before. >> >> >> >> -Takahiro AKASHI >> >> >> >>> [snip] >> >>> >> >>> Thanks >> >>> Dave > > ===8<== > From 74e2451fea83d546feae76160ba7de426913fe03 Mon Sep 17 00:00:00 2001 > From: AKASHI Takahiro <takahiro.akashi at linaro.org> > Date: Thu, 21 Dec 2017 19:14:23 +0900 > Subject: [PATCH] arm64: kdump: mark unusable memory as NOMAP > > --- > arch/arm64/mm/init.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 00e7b900ca41..8175db94257b 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -352,11 +352,17 @@ static void __init fdt_enforce_memory_region(void) > struct memblock_region reg = { > .size = 0, > }; > + u64 idx; > + phys_addr_t start, end; > > of_scan_flat_dt(early_init_dt_scan_usablemem, ®); > > - if (reg.size) > - memblock_cap_memory_range(reg.base, reg.size); > + if (reg.size) { > + for_each_free_mem_range(idx, NUMA_NO_NODE, MEMBLOCK_NONE, > + &start, &end, NULL) > + memblock_mark_nomap(start, end - start); > + memblock_clear_nomap(reg.base, reg.size); > + } > } > > void __init arm64_memblock_init(void) > -- > 2.15.1 > Thanks for the patch. After applying this on top of 4.15.0-rc4-next-20171220, there seems to be a improvement and the crashkernel boot no longer hangs while trying to access the acpi tables. However I notice a minor issue. Please see the log below for reference, the following message keeps spamming the console but I see the crashkernel boot proceed further.: [ 0.000000] ACPI: NUMA: SRAT: PXM 3 -> MPIDR 0x70303 -> Node 3 [ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0x3fffffff] [ 0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x2000000000-0x2fffffffff] [ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x1000000000-0x1fffffffff] [ 0.000000] ACPI: SRAT: Node 3 PXM 3 [mem 0xa000000000-0xafffffffff] [ 0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x9000000000-0x9fffffffff] [ 0.000000] NUMA: NODE_DATA [mem 0x1ffbffe200-0x1ffbffffff] [ 0.000000] NUMA: NODE_DATA [mem 0x1ffbffc400-0x1ffbffe1ff] [ 0.000000] NUMA: NODE_DATA(1) on node 0 [ 0.000000] NUMA: NODE_DATA [mem 0x1ffbffa600-0x1ffbffc3ff] [ 0.000000] NUMA: NODE_DATA(2) on node 0 [ 0.000000] NUMA: NODE_DATA [mem 0x1ffbff8800-0x1ffbffa5ff] [ 0.000000] NUMA: NODE_DATA(3) on node 0 [ 0.000000] [ffff7fe008000000-ffff7fe00800ffff] potential offnode page_structs [ 0.000000] [ffff7fe008010000-ffff7fe00801ffff] potential offnode page_structs [ 0.000000] [ffff7fe008020000-ffff7fe00802ffff] potential offnode page_structs [ 0.000000] [ffff7fe008030000-ffff7fe00803ffff] potential offnode page_structs [ 0.000000] [ffff7fe008040000-ffff7fe00804ffff] potential offnode page_structs [ 0.000000] [ffff7fe008050000-ffff7fe00805ffff] potential offnode page_structs [snip..] [ 0.000000] [ffff7fe0081f0000-ffff7fe0081fffff] potential offnode page_structs This WARNING message seems to come from vmemmap_verify() inside 'mm/sparse-vmemmap.c' Regards, Bhupesh
