x86/ioremap: Map EFI-reserved memory as encrypted for SEV

In the Linux kernel, the following vulnerability has been resolved:

x86/ioremap: Map EFI-reserved memory as encrypted for SEV

Some drivers require memory that is marked as EFI boot services

data. In order for this memory to not be re-used by the kernel

after ExitBootServices(), efi_mem_reserve() is used to preserve it

by inserting a new EFI memory descriptor and marking it with the

EFI_MEMORY_RUNTIME attribute.

Under SEV, memory marked with the EFI_MEMORY_RUNTIME attribute needs to

be mapped encrypted by Linux, otherwise the kernel might crash at boot

like below:

EFI Variables Facility v0.08 2004-May-17

general protection fault, probably for non-canonical address 0x3597688770a868b2: 0000 [#1] SMP NOPTI

CPU: 13 PID: 1 Comm: swapper/0 Not tainted 5.12.4-2-default #1 openSUSE Tumbleweed

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015

RIP: 0010:efi_mokvar_entry_next

[...]

Call Trace:

efi_mokvar_sysfs_init

? efi_mokvar_table_init

do_one_initcall

? __kmalloc

kernel_init_freeable

? rest_init

kernel_init

ret_from_fork

Expand the __ioremap_check_other() function to additionally check for

this other type of boot data reserved at runtime and indicate that it

should be mapped encrypted for an SEV guest.

[ bp: Massage commit message. ]