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. ]

kernel.org https://git.kernel.org/stable/c/208bb686e7fa7fff16e8fa78ff0db34aa9acdbd7 [No types assigned]

kernel.org https://git.kernel.org/stable/c/8d651ee9c71bb12fc0c8eb2786b66cbe5aa3e43b [No types assigned]

kernel.org https://git.kernel.org/stable/c/b7a05aba39f733ec337c5b952e112dd2dc4fc404 [No types assigned]