x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

The e820 table for the kexec kernel unconditionally marks setup_data as
reserved because the second kernel can reuse setup_data passed by the
1st kernel's boot loader, for example SETUP_PCI marked regions like PCI
BIOS, etc.

SETUP_EFI types, however, are used by kexec itself to enable EFI in the
2nd kernel. Thus, it is pointless to add this type of setup_data to the
kexec e820 table as reserved.

IOW, what happens is this:

  -  1st physical boot: no SETUP_EFI.

  - kexec loads a new kernel and prepares a SETUP_EFI setup_data blob, then
  reboots the machine.

  - 2nd kernel sees SETUP_EFI, reserves it both in the e820 and in the
  kexec e820 table.

  - If another kexec load is executed, it prepares a new SETUP_EFI blob and
  then reboots the machine into the new kernel.

  5. The 3rd kexec-ed kernel has two SETUP_EFI ranges reserved. And so on...

Thus skip SETUP_EFI while reserving setup_data in the e820_table_kexec
table because it is not needed.

 [ bp: Heavily massage commit message, shorten line and improve comment. ]

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200212110424.GA2938@dhcp-128-65.nay.redhat.com

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index c5399e80c59c5d2a88e1b62f4bdc8bba43be6991..c92029651b85b27dcca88a8d530ec063ba60cb79 100644 (file)
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -999,7 +999,15 @@ void __init e820__reserve_setup_data(void)
        while (pa_data) {
                data = early_memremap(pa_data, sizeof(*data));
                e820__range_update(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
-               e820__range_update_kexec(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
+
+               /*
+                * SETUP_EFI is supplied by kexec and does not need to be
+                * reserved.
+                */
+               if (data->type != SETUP_EFI)
+                       e820__range_update_kexec(pa_data,
+                                                sizeof(*data) + data->len,
+                                                E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
 
                if (data->type == SETUP_INDIRECT &&
                    ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {