Re: [RFC PATCH 1/5] efi: Detect UEFI 2.8 Special Purpose Memory

From: Ard Biesheuvel
Date: Sat Apr 06 2019 - 00:35:18 EST

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Hi Dan,

On Thu, 4 Apr 2019 at 21:21, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> 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 special 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.
>
> A follow-on patch integrates parsing of the ACPI HMAT to identify the
> node and sub-range boundaries of EFI_MEMORY_SP designated memory. For
> now, arrange for EFI_MEMORY_SP memory to be reserved.
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Cc: Darren Hart <dvhart@xxxxxxxxxxxxx>
> Cc: Andy Shevchenko <andy@xxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> arch/x86/Kconfig | 18 ++++++++++++++++++
> 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/platform/efi/efi.c | 10 +++++++++-
> include/linux/efi.h | 14 ++++++++++++++
> include/linux/ioport.h | 1 +
> 8 files changed, 63 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c1f9b3cf437c..cb9ca27de7a5 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1961,6 +1961,24 @@ config EFI_MIXED
>
> If unsure, say N.
>
> +config EFI_SPECIAL_MEMORY
> + bool "EFI Special Purpose Memory Support"
> + depends on EFI
> + ---help---
> + On systems that have mixed performance classes of memory EFI
> + may indicate special 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
> + 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. Say N to have the kernel treat this
> + memory as general purpose by default.
> +
> + If unsure, say Y.
> +

EFI_MEMORY_SP is now part of the UEFI spec proper, so it does not make
sense to make any understanding of it Kconfigurable.

Instead, what I would prefer is to implement support for EFI_MEMORY_SP
unconditionally (including the ability to identify it in the debug
dump of the memory map etc), in a way that all architectures can use
it. Then, I think we should never treat it as ordinary memory and make
it the firmware's problem not to use the EFI_MEMORY_SP attribute in
cases where it results in undesired behavior in the OS.

Also, sInce there is a generic component and a x86 component, can you
please split those up?

You only cc'ed me on patch #1 this time, but could you please cc me on
the entire series for v2? Thanks.

> 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..9b90fae21abe 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_special(d))
> + e820_type = E820_TYPE_SPECIAL;
> + 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..897e46eb9714 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_special(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..0ab8abae2e8b 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_SPECIAL = 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 2879e234e193..9f50dd0bbb04 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -176,6 +176,7 @@ 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_SPECIAL: /* Fall through: */
> 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;
> @@ -1023,6 +1024,7 @@ 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_SPECIAL: /* Fall-through: */
> case E820_TYPE_RESERVED: return "Reserved";
> default: return "Unknown E820 type";
> }
> @@ -1038,6 +1040,7 @@ 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_SPECIAL: /* Fall-through: */
> case E820_TYPE_RESERVED: /* Fall-through: */
> default: return IORESOURCE_MEM;
> }
> @@ -1050,6 +1053,7 @@ 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_SPECIAL: return IORES_DESC_APPLICATION_RESERVED;
> case E820_TYPE_RESERVED_KERN: /* Fall-through: */
> case E820_TYPE_RAM: /* Fall-through: */
> case E820_TYPE_UNUSABLE: /* Fall-through: */
> @@ -1065,13 +1069,14 @@ 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_SPECIAL:
> return false;
> case E820_TYPE_RESERVED_KERN:
> case E820_TYPE_RAM:
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index e1cb01a22fa8..d227751f331b 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -139,7 +139,9 @@ 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_special(md))
> + e820_type = E820_TYPE_SPECIAL;
> + else if (md->attribute & EFI_MEMORY_WB)
> e820_type = E820_TYPE_RAM;
> else
> e820_type = E820_TYPE_RESERVED;
> @@ -753,6 +755,12 @@ static bool should_map_region(efi_memory_desc_t *md)
> if (IS_ENABLED(CONFIG_X86_32))
> return false;
>
> + /*
> + * Special purpose memory is not mapped by default.
> + */
> + if (is_efi_special(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/efi.h b/include/linux/efi.h
> index 54357a258b35..cecbc2bda1da 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -112,6 +112,7 @@ typedef struct {
> #define EFI_MEMORY_MORE_RELIABLE \
> ((u64)0x0000000000010000ULL) /* higher reliability */
> #define EFI_MEMORY_RO ((u64)0x0000000000020000ULL) /* read-only */
> +#define EFI_MEMORY_SP ((u64)0x0000000000040000ULL) /* special purpose */
> #define EFI_MEMORY_RUNTIME ((u64)0x8000000000000000ULL) /* range requires runtime mapping */
> #define EFI_MEMORY_DESCRIPTOR_VERSION 1
>
> @@ -128,6 +129,19 @@ typedef struct {
> u64 attribute;
> } efi_memory_desc_t;
>
> +#ifdef CONFIG_EFI_SPECIAL_MEMORY
> +static inline bool is_efi_special(efi_memory_desc_t *md)
> +{
> + return md->type == EFI_CONVENTIONAL_MEMORY
> + && (md->attribute & EFI_MEMORY_SP);
> +}
> +#else
> +static inline bool is_efi_special(efi_memory_desc_t *md)
> +{
> + return false;
> +}
> +#endif
> +
> typedef struct {
> efi_guid_t guid;
> u32 headersize;
> 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 */
>

Next message: Borislav Petkov: "Re: [PATCH 1/2] x86/mm/KASLR: Fix the wrong calculation of memory region initial size"
Previous message: kernelci.org bot: "stable/linux-4.19.y boot bisection: v4.19.34 on meson-gxl-s905x-libretech-cc"
In reply to: Dan Williams: "[RFC PATCH 1/5] efi: Detect UEFI 2.8 Special Purpose Memory"
Next in thread: Dan Williams: "[RFC PATCH 2/5] lib/memregion: Uplevel the pmem "region" ida to a global allocator"
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