[PATCH] arm64: acpi: arch_apei_get_mem_attributes() should use memblock

[james.morse@arm.com (James Morse)]

arm64's arch_apei_get_mem_attributes() tries to use
efi_mem_attributes() to read the memory attributes from the efi
memory map.

drivers/firmware/efi/arm-init.c:efi_init() calls efi_memmap_unmap(),
which clears the EFI_MEMMAP bit from efi.flags once efi_init() has
finished with the memory map. This causes efi_mem_attributes() to
return 0 meaning PROT_DEVICE_nGnRnE is the chosen memory type for
all ACPI APEI mappings.

APEI may call this from NMI context, so we can't re-map the EFI
memory map as this may need to allocate virtual address space.
'ghes_ioremap_area' is APEIs cache of virtual address space to
access the buffer once we tell it the memory attributes.

Do as acpi_os_ioremap() does, and consult memblock to learn if
the provided address is memory, or not.

Signed-off-by: James Morse <james.morse@arm.com>
Cc: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
Fixes: 89e44b51cc0d ("arm64, acpi/apei: Implement arch_apei_get_mem_attributes()")

This doesn't code even get built on mainline as HAVE_ACPI_APEI isn't
defined, until https://lkml.org/lkml/2016/8/10/231 gets merged.
I don't think this should go to stable.

I also took the opportunity to remove some unnecessarily ifdef'd
includes.

 arch/arm64/kernel/acpi.c | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 252a6d9c1da5..985f721f3bdd 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -18,6 +18,7 @@
 #include <linux/acpi.h>
 #include <linux/bootmem.h>
 #include <linux/cpumask.h>
+#include <linux/efi.h>
 #include <linux/init.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
@@ -28,13 +29,9 @@
 
 #include <asm/cputype.h>
 #include <asm/cpu_ops.h>
+#include <asm/pgtable.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);
@@ -241,22 +238,13 @@ void __init acpi_boot_table_init(void)
 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.
+	 * The EFI memmap isn't mapped, instead read the version exported
+	 * into memblock. EFI's reserve_regions() call adds memory with the
+	 * WB attribute to memblock via early_init_dt_add_memory_arch().
 	 */
+	if (!memblock_is_memory(addr))
+		return __pgprot(PROT_DEVICE_nGnRnE);
 
-	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);
+	return PAGE_KERNEL;
 }
 #endif
-- 
2.10.1