arm64, acpi/apei: Implement arch_apei_get_mem_attributes()

Table 8 of UEFI 2.5 section 2.3.6.1 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.

Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
[ Small stylistic tweaks. ]
Reviewed-by: Matt Fleming <matt.fleming@intel.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1441372302-23242-2-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/arm64/include/asm/acpi.h

@@ -92,4 +92,9 @@ static inline const char *acpi_get_enable_method(int cpu)
 {
 	return acpi_psci_present() ? "psci" : NULL;
 }
+
+#ifdef	CONFIG_ACPI_APEI
+pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr);
+#endif
+
 #endif /*_ASM_ACPI_H*/

arch/arm64/kernel/acpi.c

@@ -29,6 +29,11 @@
 #include <asm/cpu_ops.h>
 #include <asm/smp_plat.h>
 
+#ifdef CONFIG_ACPI_APEI
+# include <linux/efi.h>
+# include <asm/pgtable.h>
+#endif
+
 int acpi_noirq = 1;		/* skip ACPI IRQ initialization */
 int acpi_disabled = 1;
 EXPORT_SYMBOL(acpi_disabled);
@@ -230,3 +235,27 @@ void __init acpi_gic_init(void)
 
 	early_acpi_os_unmap_memory((char *)table, tbl_size);
 }
+
+#ifdef CONFIG_ACPI_APEI
+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 2.3.6.1, each EFI memory type is
+	 * mapped to a corresponding MAIR attribute encoding.
+	 * 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);
+}
+#endif