linux-kernel - [PATCH 4.8 82/85] arm64: mark reserved memblock regions explicitly in iomem

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Date:   Wed,  4 Jan 2017 21:48:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Matthias Brugger <mbrugger@...e.com>
Subject: [PATCH 4.8 82/85] arm64: mark reserved memblock regions explicitly in iomem

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: AKASHI Takahiro <takahiro.akashi@...aro.org>

commit e7cd190385d17790cc3eb3821b1094b00aacf325 upstream.

Kdump(kexec-tools) parses /proc/iomem to identify all the memory regions
on the system. Since the current kernel names "nomap" regions, like UEFI
runtime services code/data, as "System RAM," kexec-tools sets up elf core
header to include them in a crash dump file (/proc/vmcore).

Then crash dump kernel parses UEFI memory map again, re-marks those regions
as "nomap" and does not create a memory mapping for them unlike the other
areas of System RAM. In this case, copying /proc/vmcore through
copy_oldmem_page() on crash dump kernel will end up with a kernel abort,
as reported in [1].

This patch names all the "nomap" regions explicitly as "reserved" so that
we can exclude them from a crash dump file. acpi_os_ioremap() must also
be modified because those regions have WB attributes [2].

Apart from kdump, this change also matches x86's use of acpi (and
/proc/iomem).

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/448186.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/450089.html

Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Tested-by: James Morse <james.morse@....com>
Reviewed-by: James Morse <james.morse@....com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Cc: Matthias Brugger <mbrugger@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/include/asm/acpi.h |    8 ++++++--
 arch/arm64/kernel/setup.c     |    9 +++++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -12,7 +12,7 @@
 #ifndef _ASM_ACPI_H
 #define _ASM_ACPI_H
 
-#include <linux/mm.h>
+#include <linux/memblock.h>
 #include <linux/psci.h>
 
 #include <asm/cputype.h>
@@ -32,7 +32,11 @@
 static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
 					    acpi_size size)
 {
-	if (!page_is_ram(phys >> PAGE_SHIFT))
+	/*
+	 * EFI's reserve_regions() call adds memory with the WB attribute
+	 * to memblock via early_init_dt_add_memory_arch().
+	 */
+	if (!memblock_is_memory(phys))
 		return ioremap(phys, size);
 
 	return ioremap_cache(phys, size);
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -206,10 +206,15 @@ static void __init request_standard_reso
 
 	for_each_memblock(memory, region) {
 		res = alloc_bootmem_low(sizeof(*res));
-		res->name  = "System RAM";
+		if (memblock_is_nomap(region)) {
+			res->name  = "reserved";
+			res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+		} else {
+			res->name  = "System RAM";
+			res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+		}
 		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
 		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
-		res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
 		request_resource(&iomem_resource, res);