From 816e76129ed5fadd28e526c43397c79775194b5c Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Mon, 29 Feb 2016 21:22:52 +0000 Subject: efi: Allow drivers to reserve boot services forever Today, it is not possible for drivers to reserve EFI boot services for access after efi_free_boot_services() has been called on x86. For ARM/arm64 it can be done simply by calling memblock_reserve(). Having this ability for all three architectures is desirable for a couple of reasons, 1) It saves drivers copying data out of those regions 2) kexec reboot can now make use of things like ESRT Instead of using the standard memblock_reserve() which is insufficient to reserve the region on x86 (see efi_reserve_boot_services()), a new API is introduced in this patch; efi_mem_reserve(). efi.memmap now always represents which EFI memory regions are available. On x86 the EFI boot services regions that have not been reserved via efi_mem_reserve() will be removed from efi.memmap during efi_free_boot_services(). This has implications for kexec, since it is not possible for a newly kexec'd kernel to access the same boot services regions that the initial boot kernel had access to unless they are reserved by every kexec kernel in the chain. Tested-by: Dave Young [kexec/kdump] Tested-by: Ard Biesheuvel [arm] Acked-by: Ard Biesheuvel Cc: Leif Lindholm Cc: Peter Jones Cc: Borislav Petkov Cc: Mark Rutland Signed-off-by: Matt Fleming --- drivers/firmware/efi/efi.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'drivers') diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index d4886fd50c16..dfe07316cae5 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -27,6 +27,7 @@ #include #include #include +#include #include @@ -396,6 +397,35 @@ u64 __init efi_mem_desc_end(efi_memory_desc_t *md) return end; } +void __init __weak efi_arch_mem_reserve(phys_addr_t addr, u64 size) {} + +/** + * efi_mem_reserve - Reserve an EFI memory region + * @addr: Physical address to reserve + * @size: Size of reservation + * + * Mark a region as reserved from general kernel allocation and + * prevent it being released by efi_free_boot_services(). + * + * This function should be called drivers once they've parsed EFI + * configuration tables to figure out where their data lives, e.g. + * efi_esrt_init(). + */ +void __init efi_mem_reserve(phys_addr_t addr, u64 size) +{ + if (!memblock_is_region_reserved(addr, size)) + memblock_reserve(addr, size); + + /* + * Some architectures (x86) reserve all boot services ranges + * until efi_free_boot_services() because of buggy firmware + * implementations. This means the above memblock_reserve() is + * superfluous on x86 and instead what it needs to do is + * ensure the @start, @size is not freed. + */ + efi_arch_mem_reserve(addr, size); +} + static __initdata efi_config_table_type_t common_tables[] = { {ACPI_20_TABLE_GUID, "ACPI 2.0", &efi.acpi20}, {ACPI_TABLE_GUID, "ACPI", &efi.acpi}, -- cgit v1.2.1