Re: [PATCH v6 05/12] x86/efi: EFI soft reservation to E820 enumeration

From: Ard Biesheuvel
Date: Thu Oct 10 2019 - 02:44:57 EST

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On Thu, 10 Oct 2019 at 01:19, 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 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 device-dax management scheme implements "soft" in
> the "soft reserved" designation by allowing some or all of the
> reservation to be recovered as typical memory. This policy can be
> disabled at compile-time with CONFIG_EFI_SOFT_RESERVE=n, or runtime with
> efi=nosoftreserve.
>
> 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_SOFT_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_SOFT_RESERVE=y policy is enabled, otherwise treat it as
> typical ram.
>
> - IORES_DESC_SOFT_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 "Soft 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.
>
> 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: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

For the EFI changes

Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

although I must admit I don't follow the enum add_efi_mode logic 100%

> ---
> arch/x86/boot/compressed/eboot.c | 6 ++++-
> arch/x86/boot/compressed/kaslr.c | 4 +++
> arch/x86/include/asm/e820/types.h | 8 ++++++
> arch/x86/kernel/e820.c | 12 ++++++++-
> arch/x86/platform/efi/efi.c | 48 +++++++++++++++++++++++++++++++++----
> include/linux/ioport.h | 1 +
> 6 files changed, 71 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index d6662fdef300..f3b03229c44c 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -553,7 +553,11 @@ 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 (efi_soft_reserve_enabled() &&
> + (d->attribute & EFI_MEMORY_SP))
> + e820_type = E820_TYPE_SOFT_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..ff6fa81949cd 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -760,6 +760,10 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
> if (md->type != EFI_CONVENTIONAL_MEMORY)
> continue;
>
> + if (efi_soft_reserve_enabled() &&
> + (md->attribute & EFI_MEMORY_SP))
> + continue;
> +
> if (efi_mirror_found &&
> !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
> continue;
> diff --git a/arch/x86/include/asm/e820/types.h b/arch/x86/include/asm/e820/types.h
> index c3aa4b5e49e2..314f75d886d0 100644
> --- a/arch/x86/include/asm/e820/types.h
> +++ b/arch/x86/include/asm/e820/types.h
> @@ -28,6 +28,14 @@ enum e820_type {
> */
> E820_TYPE_PRAM = 12,
>
> + /*
> + * Special-purpose 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_SOFT_RESERVED designation.
> + */
> + E820_TYPE_SOFT_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/kernel/e820.c b/arch/x86/kernel/e820.c
> index 7da2bcd2b8eb..9976106b57ec 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -190,6 +190,7 @@ static void __init e820_print_type(enum e820_type type)
> case E820_TYPE_RAM: /* Fall through: */
> case E820_TYPE_RESERVED_KERN: pr_cont("usable"); break;
> case E820_TYPE_RESERVED: pr_cont("reserved"); break;
> + case E820_TYPE_SOFT_RESERVED: pr_cont("soft reserved"); break;
> case E820_TYPE_ACPI: pr_cont("ACPI data"); break;
> case E820_TYPE_NVS: pr_cont("ACPI NVS"); break;
> case E820_TYPE_UNUSABLE: pr_cont("unusable"); break;
> @@ -1037,6 +1038,7 @@ static const char *__init e820_type_to_string(struct e820_entry *entry)
> case E820_TYPE_PRAM: return "Persistent Memory (legacy)";
> case E820_TYPE_PMEM: return "Persistent Memory";
> case E820_TYPE_RESERVED: return "Reserved";
> + case E820_TYPE_SOFT_RESERVED: return "Soft Reserved";
> default: return "Unknown E820 type";
> }
> }
> @@ -1052,6 +1054,7 @@ static unsigned long __init e820_type_to_iomem_type(struct e820_entry *entry)
> case E820_TYPE_PRAM: /* Fall-through: */
> case E820_TYPE_PMEM: /* Fall-through: */
> case E820_TYPE_RESERVED: /* Fall-through: */
> + case E820_TYPE_SOFT_RESERVED: /* Fall-through: */
> default: return IORESOURCE_MEM;
> }
> }
> @@ -1064,6 +1067,7 @@ static unsigned long __init e820_type_to_iores_desc(struct e820_entry *entry)
> case E820_TYPE_PMEM: return IORES_DESC_PERSISTENT_MEMORY;
> case E820_TYPE_PRAM: return IORES_DESC_PERSISTENT_MEMORY_LEGACY;
> case E820_TYPE_RESERVED: return IORES_DESC_RESERVED;
> + case E820_TYPE_SOFT_RESERVED: return IORES_DESC_SOFT_RESERVED;
> case E820_TYPE_RESERVED_KERN: /* Fall-through: */
> case E820_TYPE_RAM: /* Fall-through: */
> case E820_TYPE_UNUSABLE: /* Fall-through: */
> @@ -1078,11 +1082,12 @@ 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_SOFT_RESERVED:
> case E820_TYPE_PRAM:
> case E820_TYPE_PMEM:
> return false;
> @@ -1285,6 +1290,9 @@ void __init e820__memblock_setup(void)
> if (end != (resource_size_t)end)
> continue;
>
> + if (entry->type == E820_TYPE_SOFT_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/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 0bb58eb33ca0..c96657993167 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -151,10 +151,18 @@ 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_SOFT_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;
> @@ -167,7 +175,10 @@ 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 (efi_soft_reserve_enabled()
> + && (md->attribute & EFI_MEMORY_SP))
> + e820_type = E820_TYPE_SOFT_RESERVED;
> + else if (md->attribute & EFI_MEMORY_WB)
> e820_type = E820_TYPE_RAM;
> else
> e820_type = E820_TYPE_RESERVED;
> @@ -193,9 +204,17 @@ static void __init do_add_efi_memmap(void)
> e820_type = E820_TYPE_RESERVED;
> break;
> }
> +
> + if (e820_type == E820_TYPE_SOFT_RESERVED)
> + /* always add E820_TYPE_SOFT_RESERVED */;
> + else if (mode == ADD_EFI_SOFT_RESERVED)
> + continue;
> +
> + add++;
> e820__range_add(start, size, e820_type);
> }
> - e820__update_table(e820_table);
> + if (add)
> + e820__update_table(e820_table);
> }
>
> int __init efi_memblock_x86_reserve_range(void)
> @@ -227,8 +246,18 @@ int __init efi_memblock_x86_reserve_range(void)
> if (rv)
> return rv;
>
> - if (add_efi_memmap)
> - do_add_efi_memmap();
> + if (add_efi_memmap) {
> + do_add_efi_memmap(ADD_EFI_ALL);
> + } else {
> + /*
> + * Given add_efi_memmap defaults to 0 and there there is no e820
> + * mechanism for soft-reserved memory. Explicitly scan for
> + * soft-reserved memory. Otherwise, the mechanism to disable the
> + * kernel's consideration of EFI_MEMORY_SP is the
> + * efi=nosoftreserve option.
> + */
> + do_add_efi_memmap(ADD_EFI_SOFT_RESERVED);
> + }
>
> WARN(efi.memmap.desc_version != 1,
> "Unexpected EFI_MEMORY_DESCRIPTOR version %ld",
> @@ -781,6 +810,15 @@ static bool should_map_region(efi_memory_desc_t *md)
> if (IS_ENABLED(CONFIG_X86_32))
> return false;
>
> + /*
> + * EFI specific purpose memory may be reserved by default
> + * depending on kernel config and boot options.
> + */
> + if (md->type == EFI_CONVENTIONAL_MEMORY &&
> + efi_soft_reserve_enabled() &&
> + (md->attribute & EFI_MEMORY_SP))
> + 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 7bddddfc76d6..a9b9170b5dd2 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -134,6 +134,7 @@ enum {
> IORES_DESC_PERSISTENT_MEMORY_LEGACY = 5,
> IORES_DESC_DEVICE_PRIVATE_MEMORY = 6,
> IORES_DESC_RESERVED = 7,
> + IORES_DESC_SOFT_RESERVED = 8,
> };
>
> /*
>

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