Re: [PATCH 1/2] arm64: apei: implement arch_apei_get_mem_attributes()

From: Zhang, Jonathan Zhixiong
Date: Fri Aug 14 2015 - 14:55:39 EST

On 8/13/2015 1:22 AM, Ingo Molnar wrote:

* Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote:

From: "Jonathan (Zhixiong) Zhang" <zjzhang@xxxxxxxxxxxxxx>

Table 8 of UEFI 2.5 section defines mappings from EFI
memory types to MAIR attribute encodings for arm64.

If the physical address has memory attributes defined by EFI
memmap as EFI_MEMORY_[UC|WC|WT], return approprate page protection
type according to the UEFI spec. Otherwise, return PAGE_KERNEL.

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx>
arch/arm64/include/asm/acpi.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 406485ed110a..1cbad43e561d 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -19,6 +19,11 @@
#include <asm/psci.h>
#include <asm/smp_plat.h>

+#include <linux/efi.h>
+#include <asm/pgtable.h>
/* Macros for consistency checks of the GICC subtable of MADT */
(acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
@@ -92,4 +97,29 @@ static inline const char *acpi_get_enable_method(int cpu)
return acpi_psci_present() ? "psci" : NULL;
+static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
+ /*
+ * According to "Table 8 Map: EFI memory types to AArch64 memory types"
+ * of UEFI 2.5 section, each EFI memory type is mapped to
+ * corresponding MAIR attribute encoding.

s/mapped to corresponding/
mapped to a corresponding
Will do.

+ * The EFI memory attribute advises all possible capabilities of a
+ * memory region. We use the most efficient capability.
+ */
+ u64 attr;
+ attr = efi_mem_attributes(addr);
+ if (attr & EFI_MEMORY_WB)
+ return PAGE_KERNEL;
+ if (attr & EFI_MEMORY_WT)
+ return __pgprot(PROT_NORMAL_WT);
+ if (attr & EFI_MEMORY_WC)
+ return __pgprot(PROT_NORMAL_NC);
+ return __pgprot(PROT_DEVICE_nGnRnE);

Also, this doesn't look like a small function - why is it inlined?
The function grew a bit after its first version. Since it is on the
fence of not being a small function, I did not change it to out of
the line. I will move it to arch/arm64/kernel/acpi.c guarded by
CONFIG_ACPI_APEI instead of having to create a very small new file,
if there is no opposition.

Moving it to .c would also slightly improve compilation times for every .c file
that includes asm/acpi.h.



Jonathan (Zhixiong) Zhang
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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