From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Message-ID: <5A55F87F.2080501@arm.com> Date: Wed, 10 Jan 2018 11:26:55 +0000 From: James Morse MIME-Version: 1.0 Subject: Re: [PATCH] arm64: kdump: retain reserved memory regions References: <20180110100943.6082-1-takahiro.akashi@linaro.org> In-Reply-To: <20180110100943.6082-1-takahiro.akashi@linaro.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: AKASHI Takahiro , catalin.marinas@arm.com, will.deacon@arm.com Cc: dyoung@redhat.com, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org Hi Akashi, On 10/01/18 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. Ugh, because acpi_os_ioremap() looks at the efi memory map through the prism of what we pulled into memblock, which is different during kdump. Is an alternative to teach acpi_os_ioremap() to ask efi_mem_attributes() directly for the attributes to use? (e.g. arch_apei_get_mem_attribute()) > * 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. Thanks, James _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 From: james.morse@arm.com (James Morse) Date: Wed, 10 Jan 2018 11:26:55 +0000 Subject: [PATCH] arm64: kdump: retain reserved memory regions In-Reply-To: <20180110100943.6082-1-takahiro.akashi@linaro.org> References: <20180110100943.6082-1-takahiro.akashi@linaro.org> Message-ID: <5A55F87F.2080501@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Akashi, On 10/01/18 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. Ugh, because acpi_os_ioremap() looks at the efi memory map through the prism of what we pulled into memblock, which is different during kdump. Is an alternative to teach acpi_os_ioremap() to ask efi_mem_attributes() directly for the attributes to use? (e.g. arch_apei_get_mem_attribute()) > * 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. Thanks, James