Dan Williams 262b45ae3a x86/efi: EFI soft reservation to E820 enumeration ... 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". Note that the comment for do_add_efi_memmap() needed refreshing since it seemed to imply that the efi map might overflow the e820 table, but that is not an issue as of commit 7b6e4ba3cb "x86/boot/e820: Clean up the E820_X_MAX definition" that removed the 128 entry limit for e820__range_add(). 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. Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reported-by: kbuild test robot <lkp@intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> 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>		2019-11-07 15:44:14 +01:00
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api.h	kvm, x86: Properly check whether a pfn is an MMIO or not	2019-04-30 21:49:46 +02:00
types.h	x86/efi: EFI soft reservation to E820 enumeration	2019-11-07 15:44:14 +01:00