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commit 1bbc21785b7336619fb6a67f1fff5afdaf229acc upstream. Currently the sysfs interface maps the BERT error region as "memory" (through acpi_os_map_memory()) in order to copy the error records into memory buffers through memory operations (eg memory_read_from_buffer()). The OS system cannot detect whether the BERT error region is part of system RAM or it is "device memory" (eg BMC memory) and therefore it cannot detect which memory attributes the bus to memory support (and corresponding kernel mapping, unless firmware provides the required information). The acpi_os_map_memory() arch backend implementation determines the mapping attributes. On arm64, if the BERT error region is not present in the EFI memory map, the error region is mapped as device-nGnRnE; this triggers alignment faults since memcpy unaligned accesses are not allowed in device-nGnRnE regions. The ACPI sysfs code cannot therefore map by default the BERT error region with memory semantics but should use a safer default. Change the sysfs code to map the BERT error region as MMIO (through acpi_os_map_iomem()) and use the memcpy_fromio() interface to read the error region into the kernel buffer. Link: https://lore.kernel.org/linux-arm-kernel/31ffe8fc-f5ee-2858-26c5-0fd8bdd68702@arm.com Link: https://lore.kernel.org/linux-acpi/CAJZ5v0g+OVbhuUUDrLUCfX_mVqY_e8ubgLTU98=jfjTeb4t+Pw@mail.gmail.com Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Tested-by: Veronika Kabatova <vkabatov@redhat.com> Tested-by: Aristeu Rozanski <aris@redhat.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: dann frazier <dann.frazier@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.