[PATCH v2 4/8] x86, efi: Reserve UEFI 2.8 Specific Purpose Memory for dax

From: Dan Williams
Date: Thu May 30 2019 - 19:17:12 EST

UEFI 2.8 defines an EFI_MEMORY_SP attribute bit to augment the
interpretation of the EFI Memory Types as "reserved for a special
purpose".

The proposed Linux behavior for specific purpose memory is that it is
reserved for direct-access (device-dax) by default and not available for
any kernel usage, not even as an OOM fallback. Later, through udev
scripts or another init mechanism, these device-dax claimed ranges can
be reconfigured and hot-added to the available System-RAM with a unique
node identifier.

This patch introduces 3 new concepts at once given the entanglement
between early boot enumeration relative to memory that can optionally be
reserved from the kernel page allocator by default. The new concepts
are:

- E820_TYPE_SPECIFIC: Upon detecting the EFI_MEMORY_SP attribute on
EFI_CONVENTIONAL memory, update the E820 map with this new type. Only
perform this classification if the CONFIG_EFI_SPECIFIC_DAX=y policy is
enabled, otherwise treat it as typical ram.

- IORES_DESC_APPLICATION_RESERVED: Add a new I/O resource descriptor for
a device driver to search iomem resources for application specific
memory. Teach the iomem code to identify such ranges as "Application
Reserved".

- MEMBLOCK_APP_SPECIFIC: Given the memory ranges can fallback to the
traditional System RAM pool the expectation is that they will have
typical SRAT entries. In order to support a policy of device-dax by
default with the option to hotplug later, the numa initialization code
is taught to avoid marking online MEMBLOCK_APP_SPECIFIC regions.

A follow-on change integrates parsing of the ACPI HMAT to identify the
node and sub-range boundaries of EFI_MEMORY_SP designated memory. For
now, just identify and reserve memory of this type.

Cc: <x86@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Darren Hart <dvhart@xxxxxxxxxxxxx>
Cc: Andy Shevchenko <andy@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
arch/x86/Kconfig | 20 ++++++++++++++++++++
arch/x86/boot/compressed/eboot.c | 5 ++++-
arch/x86/boot/compressed/kaslr.c | 2 +-
arch/x86/include/asm/e820/types.h | 9 +++++++++
arch/x86/kernel/e820.c | 9 +++++++--
arch/x86/kernel/setup.c | 1 +
arch/x86/platform/efi/efi.c | 37 +++++++++++++++++++++++++++++++++----
drivers/acpi/numa.c | 15 ++++++++++++++-
include/linux/efi.h | 14 ++++++++++++++
include/linux/ioport.h | 1 +
include/linux/memblock.h | 7 +++++++
mm/memblock.c | 4 ++++
12 files changed, 115 insertions(+), 9 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2bbbd4d1ba31..2d58f32ed6fa 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1955,6 +1955,26 @@ config EFI_MIXED

If unsure, say N.

+config EFI_SPECIFIC_DAX
+ bool "DAX Support for EFI Specific Purpose Memory"
+ depends on EFI
+ ---help---
+ On systems that have mixed performance classes of memory EFI
+ may indicate specific purpose memory with an attribute (See
+ EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this
+ attribute may have unique performance characteristics compared
+ to the system's general purpose "System RAM" pool. On the
+ expectation that such memory has application specific usage,
+ and its base EFI memory type is "conventional" answer Y to
+ arrange for the kernel to reserve it for direct-access
+ (device-dax) by default. The memory range can later be
+ optionally assigned to the page allocator by system
+ administrator policy via the device-dax kmem facility. Say N
+ to have the kernel treat this memory as general purpose by
+ default.
+
+ If unsure, say Y.
+
config SECCOMP
def_bool y
prompt "Enable seccomp to safely compute untrusted bytecode"
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 544ac4fafd11..5afa6de508e4 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -560,7 +560,10 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
case EFI_BOOT_SERVICES_CODE:
case EFI_BOOT_SERVICES_DATA:
case EFI_CONVENTIONAL_MEMORY:
- e820_type = E820_TYPE_RAM;
+ if (is_efi_dax(d))
+ e820_type = E820_TYPE_SPECIFIC;
+ else
+ e820_type = E820_TYPE_RAM;
break;

case EFI_ACPI_MEMORY_NVS:
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 2e53c056ba20..8af8b4d4ebc9 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -757,7 +757,7 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
*
* Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free.
*/
- if (md->type != EFI_CONVENTIONAL_MEMORY)
+ if (md->type != EFI_CONVENTIONAL_MEMORY || is_efi_dax(md))
continue;

if (efi_mirror_found &&
diff --git a/arch/x86/include/asm/e820/types.h b/arch/x86/include/asm/e820/types.h
index c3aa4b5e49e2..7209e611a89d 100644
--- a/arch/x86/include/asm/e820/types.h
+++ b/arch/x86/include/asm/e820/types.h
@@ -28,6 +28,15 @@ enum e820_type {
*/
E820_TYPE_PRAM = 12,

+ /*
+ * Special-purpose / application-specific memory is indicated to
+ * the system via the EFI_MEMORY_SP attribute. Define an e820
+ * translation of this memory type for the purpose of
+ * reserving this range and marking it with the
+ * IORES_DESC_APPLICATION_RESERVED designation.
+ */
+ E820_TYPE_SPECIFIC = 0xefffffff,
+
/*
* Reserved RAM used by the kernel itself if
* CONFIG_INTEL_TXT=y is enabled, memory of this type
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 8f32e705a980..735f86594cab 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -189,6 +189,7 @@ static void __init e820_print_type(enum e820_type type)
switch (type) {
case E820_TYPE_RAM: /* Fall through: */
case E820_TYPE_RESERVED_KERN: pr_cont("usable"); break;
+ case E820_TYPE_SPECIFIC: pr_cont("application reserved"); break;
case E820_TYPE_RESERVED: pr_cont("reserved"); break;
case E820_TYPE_ACPI: pr_cont("ACPI data"); break;
case E820_TYPE_NVS: pr_cont("ACPI NVS"); break;
@@ -1036,6 +1037,7 @@ static const char *__init e820_type_to_string(struct e820_entry *entry)
case E820_TYPE_UNUSABLE: return "Unusable memory";
case E820_TYPE_PRAM: return "Persistent Memory (legacy)";
case E820_TYPE_PMEM: return "Persistent Memory";
+ case E820_TYPE_SPECIFIC: return "Application Reserved";
case E820_TYPE_RESERVED: return "Reserved";
default: return "Unknown E820 type";
}
@@ -1051,6 +1053,7 @@ static unsigned long __init e820_type_to_iomem_type(struct e820_entry *entry)
case E820_TYPE_UNUSABLE: /* Fall-through: */
case E820_TYPE_PRAM: /* Fall-through: */
case E820_TYPE_PMEM: /* Fall-through: */
+ case E820_TYPE_SPECIFIC: /* Fall-through: */
case E820_TYPE_RESERVED: /* Fall-through: */
default: return IORESOURCE_MEM;
}
@@ -1063,6 +1066,7 @@ static unsigned long __init e820_type_to_iores_desc(struct e820_entry *entry)
case E820_TYPE_NVS: return IORES_DESC_ACPI_NV_STORAGE;
case E820_TYPE_PMEM: return IORES_DESC_PERSISTENT_MEMORY;
case E820_TYPE_PRAM: return IORES_DESC_PERSISTENT_MEMORY_LEGACY;
+ case E820_TYPE_SPECIFIC: return IORES_DESC_APPLICATION_RESERVED;
case E820_TYPE_RESERVED_KERN: /* Fall-through: */
case E820_TYPE_RAM: /* Fall-through: */
case E820_TYPE_UNUSABLE: /* Fall-through: */
@@ -1078,13 +1082,14 @@ static bool __init do_mark_busy(enum e820_type type, struct resource *res)
return true;

/*
- * Treat persistent memory like device memory, i.e. reserve it
- * for exclusive use of a driver
+ * Treat persistent memory and other special memory ranges like
+ * device memory, i.e. reserve it for exclusive use of a driver
*/
switch (type) {
case E820_TYPE_RESERVED:
case E820_TYPE_PRAM:
case E820_TYPE_PMEM:
+ case E820_TYPE_SPECIFIC:
return false;
case E820_TYPE_RESERVED_KERN:
case E820_TYPE_RAM:
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 08a5f4a131f5..ddde1c7b1f9a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1109,6 +1109,7 @@ void __init setup_arch(char **cmdline_p)

if (efi_enabled(EFI_MEMMAP)) {
efi_fake_memmap();
+ efi_find_app_specific();
efi_find_mirror();
efi_esrt_init();

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index e1cb01a22fa8..899f1305c77a 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -123,10 +123,15 @@ void __init efi_find_mirror(void)
* more than the max 128 entries that can fit in the e820 legacy
* (zeropage) memory map.
*/
+enum add_efi_mode {
+ ADD_EFI_ALL,
+ ADD_EFI_APP_SPECIFIC,
+};

-static void __init do_add_efi_memmap(void)
+static void __init do_add_efi_memmap(enum add_efi_mode mode)
{
efi_memory_desc_t *md;
+ int add = 0;

for_each_efi_memory_desc(md) {
unsigned long long start = md->phys_addr;
@@ -139,7 +144,9 @@ static void __init do_add_efi_memmap(void)
case EFI_BOOT_SERVICES_CODE:
case EFI_BOOT_SERVICES_DATA:
case EFI_CONVENTIONAL_MEMORY:
- if (md->attribute & EFI_MEMORY_WB)
+ if (is_efi_dax(md))
+ e820_type = E820_TYPE_SPECIFIC;
+ else if (md->attribute & EFI_MEMORY_WB)
e820_type = E820_TYPE_RAM;
else
e820_type = E820_TYPE_RESERVED;
@@ -165,9 +172,24 @@ static void __init do_add_efi_memmap(void)
e820_type = E820_TYPE_RESERVED;
break;
}
+
+ if (e820_type == E820_TYPE_SPECIFIC) {
+ memblock_remove(start, size);
+ memblock_add_range(&memblock.reserved, start, size,
+ MAX_NUMNODES, MEMBLOCK_APP_SPECIFIC);
+ } else if (mode != ADD_EFI_APP_SPECIFIC)
+ continue;
+
+ add++;
e820__range_add(start, size, e820_type);
}
- e820__update_table(e820_table);
+ if (add)
+ e820__update_table(e820_table);
+}
+
+void __init efi_find_app_specific(void)
+{
+ do_add_efi_memmap(ADD_EFI_APP_SPECIFIC);
}

int __init efi_memblock_x86_reserve_range(void)
@@ -200,7 +222,7 @@ int __init efi_memblock_x86_reserve_range(void)
return rv;

if (add_efi_memmap)
- do_add_efi_memmap();
+ do_add_efi_memmap(ADD_EFI_ALL);

WARN(efi.memmap.desc_version != 1,
"Unexpected EFI_MEMORY_DESCRIPTOR version %ld",
@@ -753,6 +775,13 @@ static bool should_map_region(efi_memory_desc_t *md)
if (IS_ENABLED(CONFIG_X86_32))
return false;

+ /*
+ * Specific purpose memory assigned to device-dax is
+ * not mapped by default.
+ */
+ if (is_efi_dax(md))
+ return false;
+
/*
* Map all of RAM so that we can access arguments in the 1:1
* mapping when making EFI runtime calls.
diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index 30995834ad70..9083bb8f611b 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -260,7 +260,7 @@ void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
int __init
acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
{
- u64 start, end;
+ u64 start, end, i, a_start, a_end;
u32 hotpluggable;
int node, pxm;

@@ -283,6 +283,19 @@ acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
if (acpi_srat_revision <= 1)
pxm &= 0xff;

+ /* Clamp Application Specific Memory */
+ for_each_mem_range(i, &memblock.reserved, NULL, NUMA_NO_NODE,
+ MEMBLOCK_APP_SPECIFIC, &a_start, &a_end, NULL) {
+ pr_debug("%s: SP: %#llx %#llx SRAT: %#llx %#llx\n", __func__,
+ a_start, a_end, start, end);
+ if (a_start <= start && a_end >= end)
+ goto out_err;
+ if (a_start >= start && a_start < end)
+ start = a_start;
+ if (a_end <= end && end > start)
+ end = a_end;
+ }
+
node = acpi_map_pxm_to_node(pxm);
if (node == NUMA_NO_NODE || node >= MAX_NUMNODES) {
pr_err("SRAT: Too many proximity domains.\n");
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 91368f5ce114..b57b123cbdf9 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -129,6 +129,19 @@ typedef struct {
u64 attribute;
} efi_memory_desc_t;

+#ifdef CONFIG_EFI_SPECIFIC_DAX
+static inline bool is_efi_dax(efi_memory_desc_t *md)
+{
+ return md->type == EFI_CONVENTIONAL_MEMORY
+ && (md->attribute & EFI_MEMORY_SP);
+}
+#else
+static inline bool is_efi_dax(efi_memory_desc_t *md)
+{
+ return false;
+}
+#endif
+
typedef struct {
efi_guid_t guid;
u32 headersize;
@@ -1043,6 +1056,7 @@ extern efi_status_t efi_query_variable_store(u32 attributes,
unsigned long size,
bool nonblocking);
extern void efi_find_mirror(void);
+extern void efi_find_app_specific(void);
#else

static inline efi_status_t efi_query_variable_store(u32 attributes,
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index da0ebaec25f0..2d79841ee9b9 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -133,6 +133,7 @@ enum {
IORES_DESC_PERSISTENT_MEMORY_LEGACY = 5,
IORES_DESC_DEVICE_PRIVATE_MEMORY = 6,
IORES_DESC_DEVICE_PUBLIC_MEMORY = 7,
+ IORES_DESC_APPLICATION_RESERVED = 8,
};

/* helpers to define resources */
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 676d3900e1bd..58c29180f2cd 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -35,12 +35,14 @@ extern unsigned long long max_possible_pfn;
* @MEMBLOCK_HOTPLUG: hotpluggable region
* @MEMBLOCK_MIRROR: mirrored region
* @MEMBLOCK_NOMAP: don't add to kernel direct mapping
+ * @MEMBLOCK_APP_SPECIFIC: reserved / application specific range
*/
enum memblock_flags {
MEMBLOCK_NONE = 0x0, /* No special request */
MEMBLOCK_HOTPLUG = 0x1, /* hotpluggable region */
MEMBLOCK_MIRROR = 0x2, /* mirrored region */
MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
+ MEMBLOCK_APP_SPECIFIC = 0x8, /* reserved / application specific range */
};

/**
@@ -215,6 +217,11 @@ static inline bool memblock_is_mirror(struct memblock_region *m)
return m->flags & MEMBLOCK_MIRROR;
}

+static inline bool memblock_is_app_specific(struct memblock_region *m)
+{
+ return m->flags & MEMBLOCK_APP_SPECIFIC;
+}
+
static inline bool memblock_is_nomap(struct memblock_region *m)
{
return m->flags & MEMBLOCK_NOMAP;
diff --git a/mm/memblock.c b/mm/memblock.c
index 6bbad46f4d2c..654fecb52ba5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -982,6 +982,10 @@ static bool should_skip_region(struct memblock_region *m, int nid, int flags)
if ((flags & MEMBLOCK_MIRROR) && !memblock_is_mirror(m))
return true;

+ /* if we want specific memory skip non-specific memory regions */
+ if ((flags & MEMBLOCK_APP_SPECIFIC) && !memblock_is_app_specific(m))
+ return true;
+
/* skip nomap memory unless we were asked for it explicitly */
if (!(flags & MEMBLOCK_NOMAP) && memblock_is_nomap(m))
return true;