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Subject[PATCH v4 05/10] x86, efi: Reserve UEFI 2.8 Specific Purpose Memory for dax
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UEFI 2.8 defines an EFI_MEMORY_SP attribute bit to augment the
interpretation of the EFI Memory Types as "reserved for a specific
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 2 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_APPLICATION_RESERVED: 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".

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.

For now this translation of EFI_CONVENTIONAL + EFI_MEMORY_SP is
x86/E820-only, but other archs could choose to publish
IORES_DESC_APPLICATION_RESERVED resources from their platform-firmware
memory map handlers.

Cc: <x86@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Andy Shevchenko <andy@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
arch/x86/Kconfig | 23 +++++++++++++++++++++++
arch/x86/boot/compressed/eboot.c | 5 ++++-
arch/x86/boot/compressed/kaslr.c | 3 ++-
arch/x86/include/asm/e820/types.h | 9 +++++++++
arch/x86/include/asm/efi.h | 17 +++++++++++++++++
arch/x86/kernel/e820.c | 12 ++++++++++--
arch/x86/kernel/setup.c | 1 +
arch/x86/platform/efi/efi.c | 37 +++++++++++++++++++++++++++++++++----
include/linux/ioport.h | 1 +
9 files changed, 100 insertions(+), 8 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2bbbd4d1ba31..d8d3b4e87ac1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1955,6 +1955,29 @@ config EFI_MIXED

If unsure, say N.

+config EFI_APPLICATION_RESERVED
+ bool "Reserve EFI Specific Purpose Memory"
+ depends on ACPI_HMAT
+ default ACPI_HMAT
+ 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 as an "Application
+ Reserved" resource, and set aside 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 "System RAM" 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..a6c96eb6e633 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_application_reserved(d))
+ e820_type = E820_TYPE_APPLICATION_RESERVED;
+ 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..e8306f452182 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -757,7 +757,8 @@ 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_application_reserved(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..41193c116a1f 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_APPLICATION_RESERVED = 0xefffffff,
+
/*
* Reserved RAM used by the kernel itself if
* CONFIG_INTEL_TXT=y is enabled, memory of this type
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 7d52378e376a..4f80254e0541 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -141,6 +141,19 @@ extern void efi_switch_mm(struct mm_struct *mm);
extern void efi_recover_from_page_fault(unsigned long phys_addr);
extern void efi_free_boot_services(void);

+#ifdef CONFIG_EFI_APPLICATION_RESERVED
+static inline bool is_efi_application_reserved(efi_memory_desc_t *md)
+{
+ return md->type == EFI_CONVENTIONAL_MEMORY
+ && (md->attribute & EFI_MEMORY_SP);
+}
+#else
+static inline bool is_efi_application_reserved(efi_memory_desc_t *md)
+{
+ return false;
+}
+#endif
+
struct efi_setup_data {
u64 fw_vendor;
u64 runtime;
@@ -244,6 +257,7 @@ extern bool efi_reboot_required(void);

extern void efi_find_mirror(void);
extern void efi_reserve_boot_services(void);
+extern void __init efi_find_application_reserved(void);
#else
static inline void parse_efi_setup(u64 phys_addr, u32 data_len) {}
static inline bool efi_reboot_required(void)
@@ -256,6 +270,9 @@ static inline void efi_find_mirror(void)
static inline void efi_reserve_boot_services(void)
{
}
+static inline void __init efi_find_application_reserved(void)
+{
+}
#endif /* CONFIG_EFI */

#endif /* _ASM_X86_EFI_H */
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 8f32e705a980..c5b91c2d0661 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_APPLICATION_RESERVED: 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_APPLICATION_RESERVED: 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_APPLICATION_RESERVED: /* 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_APPLICATION_RESERVED: 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_APPLICATION_RESERVED:
return false;
case E820_TYPE_RESERVED_KERN:
case E820_TYPE_RAM:
@@ -1285,6 +1290,9 @@ void __init e820__memblock_setup(void)
if (end != (resource_size_t)end)
continue;

+ if (entry->type == E820_TYPE_APPLICATION_RESERVED)
+ memblock_reserve(entry->addr, entry->size);
+
if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN)
continue;

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index b68fd57a8d26..3b9001b7c951 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1104,6 +1104,7 @@ void __init setup_arch(char **cmdline_p)

memblock_set_current_limit(ISA_END_ADDRESS);

+ efi_find_application_reserved();
e820__memblock_setup();

reserve_bios_regions();
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 4e8458b1ca30..4b4a9eb6d2c9 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -126,10 +126,18 @@ 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_APPLICATION_RESERVED,
+};

-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;
+
+ if (!efi_enabled(EFI_MEMMAP))
+ return;

for_each_efi_memory_desc(md) {
unsigned long long start = md->phys_addr;
@@ -142,7 +150,9 @@ 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_application_reserved(md))
+ e820_type = E820_TYPE_APPLICATION_RESERVED;
+ else if (md->attribute & EFI_MEMORY_WB)
e820_type = E820_TYPE_RAM;
else
e820_type = E820_TYPE_RESERVED;
@@ -168,9 +178,22 @@ static void __init do_add_efi_memmap(void)
e820_type = E820_TYPE_RESERVED;
break;
}
+
+ if (e820_type == E820_TYPE_APPLICATION_RESERVED)
+ /* always add E820_TYPE_APPLICATION_RESERVED */;
+ else if (mode != ADD_EFI_APPLICATION_RESERVED)
+ 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_application_reserved(void)
+{
+ do_add_efi_memmap(ADD_EFI_APPLICATION_RESERVED);
}

int __init efi_memblock_x86_reserve_range(void)
@@ -203,7 +226,7 @@ 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",
@@ -756,6 +779,12 @@ static bool should_map_region(efi_memory_desc_t *md)
if (IS_ENABLED(CONFIG_X86_32))
return false;

+ /*
+ * Specific purpose memory is reserved by default.
+ */
+ if (is_efi_application_reserved(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/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 */
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