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efi: Common enable/disable infrastructure for EFI soft reservation

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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.

As for this patch, define the common helpers to determine if the
EFI_MEMORY_SP attribute should be honored. The determination needs to be
made early to prevent the kernel from being loaded into soft-reserved
memory, or otherwise allowing early allocations to land there. Follow-on
changes are needed per architecture to leverage these helpers in their
respective mem-init paths.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Dan Williams
2019-11-06 17:43:11 -08:00
committed by Rafael J. Wysocki
parent 6950e31b35
commit b617c5266e
5 changed files with 70 additions and 1 deletions
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9
Documentation/admin-guide/kernel-parameters.txt
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@@ -1168,7 +1168,8 @@
Format: {"off" | "on" | "skip[mbr]"}
efi= [EFI]
Format: { "old_map", "nochunk", "noruntime", "debug" }
Format: { "old_map", "nochunk", "noruntime", "debug",
"nosoftreserve" }
old_map [X86-64]: switch to the old ioremap-based EFI
runtime services mapping. 32-bit still uses this one by
default.
@@ -1177,6 +1178,12 @@
firmware implementations.
noruntime : disable EFI runtime services support
debug: enable misc debug output
nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
attribute may cause the kernel to reserve the
memory range for a memory mapping driver to
claim. Specify efi=nosoftreserve to disable this
reservation and treat the memory by its base type
(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
efi_no_storage_paranoia [EFI; X86]
Using this parameter you can use more than 50% of