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 ...] >> 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? > >> >> >> 6b). The kernel code currently looks like the following: >> >> >> >> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c >> >> index 30ad2f085d1f..867bdec7c692 100644 >> >> --- a/arch/arm64/kernel/setup.c >> >> +++ b/arch/arm64/kernel/setup.c >> >> @@ -206,6 +206,7 @@ static void __init request_standard_resources(void) >> >> { >> >> struct memblock_region *region; >> >> struct resource *res; >> >> + phys_addr_t addr_start, addr_end; >> >> >> >> kernel_code.start = __pa_symbol(_text); >> >> kernel_code.end = __pa_symbol(__init_begin - 1); >> >> @@ -218,9 +219,17 @@ static void __init request_standard_resources(void) >> >> res->name = "reserved"; >> >> res->flags = IORESOURCE_MEM; >> >> } else { >> >> - res->name = "System RAM"; >> >> - res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; >> >> + addr_start = >> >> __pfn_to_phys(memblock_region_reserved_base_pfn(region)); >> >> + addr_end = >> >> __pfn_to_phys(memblock_region_reserved_end_pfn(region)) - 1; >> >> + if ((efi_mem_type(addr_start) == EFI_ACPI_RECLAIM_MEMORY) >> >> || (efi_mem_type(addr_end) == EFI_ACPI_RECLAIM_MEMORY)) { >> >> + res->name = "ACPI reclaim region"; >> >> + res->flags = IORESOURCE_MEM; >> >> + } else { >> >> + res->name = "System RAM"; >> >> + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; >> >> + } >> >> } >> >> + >> >> res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region)); >> >> res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1; >> >> >> >> @@ -292,6 +301,7 @@ void __init setup_arch(char **cmdline_p) >> >> >> >> request_standard_resources(); >> >> >> >> + efi_memmap_unmap(); >> >> early_ioremap_reset(); >> >> >> >> if (acpi_disabled) >> >> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c >> >> index 80d1a885def5..a7c522eac640 100644 >> >> --- a/drivers/firmware/efi/arm-init.c >> >> +++ b/drivers/firmware/efi/arm-init.c >> >> @@ -259,7 +259,6 @@ void __init efi_init(void) >> >> >> >> reserve_regions(); >> >> efi_esrt_init(); >> >> - efi_memmap_unmap(); >> >> >> >> memblock_reserve(params.mmap & PAGE_MASK, >> >> PAGE_ALIGN(params.mmap_size + >> >> >> >> >> >> After this change the ACPI reclaim regions are properly recognized in >> >> '/proc/iomem': >> >> >> >> # cat /proc/iomem | grep -i ACPI >> >> 396c0000-3975ffff : ACPI reclaim region >> >> 39770000-397affff : ACPI reclaim region >> >> 398a0000-398bffff : ACPI reclaim region >> >> >> >> 6c). I am currently changing the 'kexec-tools' and will finish the >> >> testing over the next few days. >> >> >> >> I just wanted to know your opinion on this issue, so that I will be >> >> able to propose a fix on the above lines. >> >> >> >> Also Cc'ing kexec mailing list for more inputs on changes proposed to >> >> kexec-tools. >> >> >> >> Thanks, >> >> Bhupesh -- 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
