[PATCH 3/3] x86: add support for the non-standard protected e820 type

[Christoph Hellwig <hch@lst.de>]

Various recent bioses support NVDIMMs or ADR using a non-standard
e820 memory type, and Intel supplied reference Linux code using this
type to various vendors.

Wire this e820 table type up to export platform devices for the pmem
driver so that we can use it in Linux, and also provide a memmap=
argument to manually tag memory as protected, which can be used
if the bios doesn't use the standard nonstandard interface, or
we just want to test the pmem driver with regular memory.

Based on an earlier patch from Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/kernel-parameters.txt |  6 ++++
 arch/x86/Kconfig                    | 13 +++++++
 arch/x86/include/asm/setup.h        |  6 ++++
 arch/x86/include/uapi/asm/e820.h    | 10 ++++++
 arch/x86/kernel/Makefile            |  1 +
 arch/x86/kernel/e820.c              | 22 +++++++++++-
 arch/x86/kernel/pmem.c              | 70 +++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/setup.c             |  2 ++
 8 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/kernel/pmem.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a6..98eeaca 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1965,6 +1965,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			         or
 			         memmap=0x10000$0x18690000
 
+	memmap=nn[KMG]!ss[KMG]
+			[KNL,X86] Mark specific memory as protected.
+			Region of memory to be used, from ss to ss+nn.
+			The memory region may be marked as type 12 and
+			is NVDIMM or ADR memory.
+
 	memory_corruption_check=0/1 [X86]
 			Some BIOSes seem to corrupt the first 64k of
 			memory when doing things like suspend/resume.
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b7d31ca..93a27e4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1430,6 +1430,19 @@ config ILLEGAL_POINTER_VALUE
 
 source "mm/Kconfig"
 
+config X86_PMEM_LEGACY
+	bool "Support non-stanard NVDIMMs and ADR protected memory"
+	help
+	  Treat memory marked using the non-stard e820 type of 12 as used
+	  by the Intel Sandy Bridge-EP reference BIOS as protected memory.
+	  The kernel will the offer these regions to the pmem driver so
+	  they can be used for persistent storage.
+
+	  If you say N the kernel will treat the ADR region like an e820
+	  reserved region.
+
+	  Say Y if unsure
+
 config HIGHPTE
 	bool "Allocate 3rd-level pagetables from highmem"
 	depends on HIGHMEM
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index ff4e7b2..2352fde 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -57,6 +57,12 @@ extern void x86_ce4100_early_setup(void);
 static inline void x86_ce4100_early_setup(void) { }
 #endif
 
+#ifdef CONFIG_X86_PMEM_LEGACY
+void reserve_pmem(void);
+#else
+static inline void reserve_pmem(void) { }
+#endif
+
 #ifndef _SETUP
 
 #include <asm/espfix.h>
diff --git a/arch/x86/include/uapi/asm/e820.h b/arch/x86/include/uapi/asm/e820.h
index d993e33..e040950 100644
--- a/arch/x86/include/uapi/asm/e820.h
+++ b/arch/x86/include/uapi/asm/e820.h
@@ -33,6 +33,16 @@
 #define E820_NVS	4
 #define E820_UNUSABLE	5
 
+/*
+ * This is a non-standardized way to represent ADR or NVDIMM regions that
+ * persist over a reboot.  The kernel will ignore their special capabilities
+ * unless the CONFIG_X86_PMEM_LEGACY option is set.
+ *
+ * Note that older platforms also used 6 for the same type of memory,
+ * but newer versions switched to 12 as 6 was assigned differently.  Some
+ * time they will learn..
+ */
+#define E820_PROTECTED_KERN	12
 
 /*
  * reserved RAM used by kernel itself
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index cdb1b70..971f18c 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -94,6 +94,7 @@ obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvmclock.o
 obj-$(CONFIG_PARAVIRT)		+= paravirt.o paravirt_patch_$(BITS).o
 obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= paravirt-spinlocks.o
 obj-$(CONFIG_PARAVIRT_CLOCK)	+= pvclock.o
+obj-$(CONFIG_X86_PMEM_LEGACY)	+= pmem.o
 
 obj-$(CONFIG_PCSPKR_PLATFORM)	+= pcspeaker.o
 
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index de088e3..8c6a976 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -48,10 +48,22 @@ unsigned long pci_mem_start = 0xaeedbabe;
 EXPORT_SYMBOL(pci_mem_start);
 #endif
 
+/*
+ * Memory protected by the system ADR (asynchronous dram refresh)
+ * mechanism is accounted as ram for purposes of establishing max_pfn
+ * and mem_map.
+ */
+#ifdef CONFIG_X86_PMEM_LEGACY
+static inline bool is_e820_ram(__u32 type)
+{
+	return type == E820_RAM || type == E820_PROTECTED_KERN;
+}
+#else
 static inline bool is_e820_ram(__u32 type)
 {
 	return type == E820_RAM;
 }
+#endif
 
 /*
  * This function checks if any part of the range <start,end> is mapped
@@ -154,6 +166,9 @@ static void __init e820_print_type(u32 type)
 	case E820_UNUSABLE:
 		printk(KERN_CONT "unusable");
 		break;
+	case E820_PROTECTED_KERN:
+		printk(KERN_CONT "protected (type %u)\n", type);
+		break;
 	default:
 		printk(KERN_CONT "type %u", type);
 		break;
@@ -871,6 +886,9 @@ static int __init parse_memmap_one(char *p)
 	} else if (*p == '$') {
 		start_at = memparse(p+1, &p);
 		e820_add_region(start_at, mem_size, E820_RESERVED);
+	} else if (*p == '!') {
+		start_at = memparse(p+1, &p);
+		e820_add_region(start_at, mem_size, E820_PROTECTED_KERN);
 	} else
 		e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
 
@@ -912,6 +930,7 @@ static inline const char *e820_type_to_string(int e820_type)
 	case E820_ACPI:	return "ACPI Tables";
 	case E820_NVS:	return "ACPI Non-volatile Storage";
 	case E820_UNUSABLE:	return "Unusable memory";
+	case E820_PROTECTED_KERN: return "Protected RAM";
 	default:	return "reserved";
 	}
 }
@@ -946,7 +965,8 @@ void __init e820_reserve_resources(void)
 		 * pcibios_resource_survey()
 		 */
 		if (e820.map[i].type != E820_RESERVED || res->start < (1ULL<<20)) {
-			res->flags |= IORESOURCE_BUSY;
+			if (e820.map[i].type != E820_PROTECTED_KERN)
+				res->flags |= IORESOURCE_BUSY;
 			insert_resource(&iomem_resource, res);
 		}
 		res++;
diff --git a/arch/x86/kernel/pmem.c b/arch/x86/kernel/pmem.c
new file mode 100644
index 0000000..902e2f9
--- /dev/null
+++ b/arch/x86/kernel/pmem.c
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2009, Intel Corporation.
+ * Copyright (c) 2015, Christoph Hellwig.
+ */
+#include <linux/memblock.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <asm/e820.h>
+#include <asm/page_types.h>
+#include <asm/setup.h>
+
+void __init reserve_pmem(void)
+{
+	int i;
+
+	for (i = 0; i < e820.nr_map; i++) {
+		struct e820entry *ei = &e820.map[i];
+
+		if (ei->type != E820_PROTECTED_KERN)
+			continue;
+
+		memblock_reserve(ei->addr, ei->addr + ei->size);
+		max_pfn_mapped = init_memory_mapping(
+				ei->addr < 1UL << 32 ? 1UL << 32 : ei->addr,
+				ei->addr + ei->size);
+	}
+}
+		
+static __init void register_pmem_device(struct resource *res)
+{
+	struct platform_device *pdev;
+	int error;
+
+	pdev = platform_device_alloc("pmem", PLATFORM_DEVID_AUTO);
+	if (!pdev)
+		return;
+
+	error = platform_device_add_resources(pdev, res, 1);
+	if (error)
+		goto out_put_pdev;
+
+	error = platform_device_add(pdev);
+	if (error)
+		goto out_put_pdev;
+	return;
+out_put_pdev:
+	dev_warn(&pdev->dev, "failed to add pmem device!\n");
+	platform_device_put(pdev);
+}
+
+static __init int register_pmem_devices(void)
+{
+	int i;
+
+	for (i = 0; i < e820.nr_map; i++) {
+		struct e820entry *ei = &e820.map[i];
+
+		if (ei->type == E820_PROTECTED_KERN) {
+			struct resource res = {
+				.flags	= IORESOURCE_MEM,
+				.start	= ei->addr,
+				.end	= ei->addr + ei->size - 1,
+			};
+			register_pmem_device(&res);
+		}
+	}
+
+	return 0;
+}
+device_initcall(register_pmem_devices);
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0a2421c..f2bed2b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1158,6 +1158,8 @@ void __init setup_arch(char **cmdline_p)
 
 	early_acpi_boot_init();
 
+	reserve_pmem();
+
 	initmem_init();
 	dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);
 
-- 
1.9.1