From: "Jonathan (Zhixiong) Zhang" zjzhang@codeaurora.org
On a platform with APEI (ACPI Platform Error Interface) enabled, firmware updates a memory region with hardware error record using nocache attribute. When OS reads the region, since it maps the region with cacahed attribute even though EFI memory map defines this region as uncached, OS gets stale data and errorneously reports there is no new HW error.
When ghes driver maps the memory region, it uses the cache attribute according to EFI memory map, if EFI memory map feature is enabled at runtime.
Since both arch/x86 and arch/ia64 implemented architecture agnostic EFI memory map attribue lookup function efi_memattributes(), the code is moved from arch/x86 into EFI subsystem and is declared as __weak; archs other than ia64 should not override the default implementation.
V3: 1. Rebased to v4.1-rc7. 2. Moved efi_mem_attributes() from arch/x86 to drivers/firmware/efi and declared it as __weak. 3. Introduced ARCH_APEI_PAGE_KERNEL_UC to allow arch specific page protection type for UC. 4. Removed efi_ioremap(). It can not be used for GHES memory region mapping purpose since ioremap can not be used in atomic context.
V2: 1. Rebased to v4.1-rc5. 2. Split removal of efi_mem_attributes() and creation of efi_ioremap() into two patches.
Jonathan (Zhixiong) Zhang (4): x86: acpi: define uncached page flag arm64: acpi: define uncached page flag efi: x86: rearrange efi_mem_attributes() acpi, apei: use EFI memmap to map GHES memory
arch/arm64/include/asm/acpi.h | 4 ++++ arch/x86/include/asm/acpi.h | 4 ++++ arch/x86/platform/efi/efi.c | 18 ------------------ drivers/acpi/apei/ghes.c | 9 ++++++++- drivers/firmware/efi/efi.c | 18 ++++++++++++++++++ 5 files changed, 34 insertions(+), 19 deletions(-)