x86/efi: Don't try to reserve runtime regions

Reserving a runtime region results in splitting the EFI memory
descriptors for the runtime region. This results in runtime region
descriptors with bogus memory mappings, leading to interesting crashes
like the following during a kexec:

  general protection fault: 0000 [#1] SMP
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0-rc1 #53
  Hardware name: Wiwynn Leopard-Orv2/Leopard-DDR BW, BIOS LBM05   09/30/2016
  RIP: 0010:virt_efi_set_variable()
  ...
  Call Trace:
   efi_delete_dummy_variable()
   efi_enter_virtual_mode()
   start_kernel()
   ? set_init_arg()
   x86_64_start_reservations()
   x86_64_start_kernel()
   start_cpu()
  ...
  Kernel panic - not syncing: Fatal exception

Runtime regions will not be freed and do not need to be reserved, so
skip the memmap modification in this case.

Signed-off-by: Omar Sandoval <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
Cc: <[email protected]> # v4.9+
Cc: Ard Biesheuvel <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Jones <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Fixes: 8e80632 ("efi/esrt: Use efi_mem_reserve() and avoid a kmalloc()")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

arch/x86/platform/efi/quirks.c

@@ -201,6 +201,10 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 		return;
 	}
 
+	/* No need to reserve regions that will never be freed. */
+	if (md.attribute & EFI_MEMORY_RUNTIME)
+		return;
+
 	size += addr % EFI_PAGE_SIZE;
 	size = round_up(size, EFI_PAGE_SIZE);
 	addr = round_down(addr, EFI_PAGE_SIZE);