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

[Ard Biesheuvel]

(cc Mike for memblock)

On Fri, 31 May 2019 at 01:13, 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 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.
>

OK, so now we have 'special purpose', 'specific' and 'app specific'
[below]. Do they all mean the same thing?

> - 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.
>

Can we move the generic memblock changes into a separate patch please?

> 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;

I'd prefer it if we could avoid this DAX policy distinction leaking
into the EFI layer.

IOW, I am fine with having a 'is_efi_sp_memory()' helper here, but
whether that is DAX memory or not should be decided in the DAX layer.

> @@ -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;
>