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efi: Allow drivers to reserve boot services forever

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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 <[email protected]> [kexec/kdump]
Tested-by: Ard Biesheuvel <[email protected]> [arm]
Acked-by: Ard Biesheuvel <[email protected]>
Cc: Leif Lindholm <[email protected]>
Cc: Peter Jones <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
This commit is contained in:
Matt Fleming 2016-02-29 21:22:52 +00:00
commit 816e76129e
3 changed files with 141 additions and 11 deletions
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30
drivers/firmware/efi/efi.c
View file

@ -27,6 +27,7 @@
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/ucs2_string.h>
#include <linux/memblock.h>
#include <asm/early_ioremap.h>
@ -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},