From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Thu, 11 Jan 2018 20:32:03 +0900 Subject: [PATCH] arm64: kdump: retain reserved memory regions In-Reply-To: References: <20180110100943.6082-1-takahiro.akashi@linaro.org> Message-ID: <20180111113202.GE18820@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jan 10, 2018 at 11:09:32AM +0000, Ard Biesheuvel wrote: > On 10 January 2018 at 10:09, AKASHI Takahiro wrote: > > This is a fix against the issue that crash dump kernel may hang up > > during booting, which can happen on any ACPI-based system with "ACPI > > Reclaim Memory." > > > > > > Bye! > > (snip...) > > ACPI: Core revision 20170728 > > pud=000000002e7d0003, *pmd=000000002e7c0003, *pte=00e8000039710707 > > Internal error: Oops: 96000021 [#1] SMP > > Modules linked in: > > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc6 #1 > > task: ffff000008d05180 task.stack: ffff000008cc0000 > > PC is at acpi_ns_lookup+0x25c/0x3c0 > > LR is at acpi_ds_load1_begin_op+0xa4/0x294 > > (snip...) > > Process swapper/0 (pid: 0, stack limit = 0xffff000008cc0000) > > Call trace: > > (snip...) > > [] acpi_ns_lookup+0x25c/0x3c0 > > [] acpi_ds_load1_begin_op+0xa4/0x294 > > [] acpi_ps_build_named_op+0xc4/0x198 > > [] acpi_ps_create_op+0x14c/0x270 > > [] acpi_ps_parse_loop+0x188/0x5c8 > > [] acpi_ps_parse_aml+0xb0/0x2b8 > > [] acpi_ns_one_complete_parse+0x144/0x184 > > [] acpi_ns_parse_table+0x48/0x68 > > [] acpi_ns_load_table+0x4c/0xdc > > [] acpi_tb_load_namespace+0xe4/0x264 > > [] acpi_load_tables+0x48/0xc0 > > [] acpi_early_init+0x9c/0xd0 > > [] start_kernel+0x3b4/0x43c > > Code: b9008fb9 2a000318 36380054 32190318 (b94002c0) > > ---[ end trace c46ed37f9651c58e ]--- > > Kernel panic - not syncing: Fatal exception > > Rebooting in 10 seconds.. > > > > (diagnosis) > > * This fault is a data abort, alignment fault (ESR=0x96000021) > > during reading out ACPI table. > > * Initial ACPI tables are normally stored in system ram and marked as > > "ACPI Reclaim memory" by the firmware. > > * After the commit f56ab9a5b73c ("efi/arm: Don't mark ACPI reclaim > > memory as MEMBLOCK_NOMAP"), those regions' attribute were changed > > removing NOMAP bit and they are instead "memblock-reserved". > > * When crash dump kernel boots up, it tries to accesses ACPI tables by > > ioremap'ing them (through acpi_os_ioremap()). > > * Since those regions are not included in device tree's > > "usable-memory-range" and so not recognized as part of crash dump > > kernel's system ram, ioremap() will create a non-cacheable mapping here. > > * ACPI accessor/helper functions are compiled in without unaligned access > > support (ACPI_MISALIGNMENT_NOT_SUPPORTED), eventually ending up a fatal > > panic when accessing ACPI tables. > > > > With this patch, all the reserved memory regions, as well as NOMAP- > > attributed ones which are presumably ACPI runtime code and data, are set > > to be retained in system ram even if they are outside of usable memory > > range specified by device tree blob. Accordingly, ACPI tables are mapped > > as cacheable and can be safely accessed without causing unaligned access > > faults. > > > > Reported-by: Bhupesh Sharma > > Signed-off-by: AKASHI Takahiro > > --- > > arch/arm64/mm/init.c | 16 ++++++++++++++-- > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > index 2d5a443b205c..e4a8b64a09b1 100644 > > --- a/arch/arm64/mm/init.c > > +++ b/arch/arm64/mm/init.c > > @@ -352,11 +352,23 @@ 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); > > Given that memblock_cap_memory_range() was introduced by you for > kdump, is there any way to handle it there? Indeed, but I'm not sure that the new semantics of this function is quite generic. > If not, should we remove it? I prefer to remove it. Thanks, -Takahiro AKASHI > > + if (reg.size) { > > +retry: > > + /* exclude usable & !reserved memory */ > > + for_each_free_mem_range(idx, NUMA_NO_NODE, MEMBLOCK_NONE, > > + &start, &end, NULL) { > > + memblock_remove(start, end - start); > > + goto retry; > > + } > > + > > + /* add back fdt's usable memory */ > > + memblock_add(reg.base, reg.size); > > + } > > } > > > > void __init arm64_memblock_init(void) > > -- > > 2.15.1 > >