x86/boot: Disable RSDP parsing temporarily

The original intention to move RDSP parsing very early, before KASLR
does its ranges selection, was to accommodate movable memory regions
machines (CONFIG_MEMORY_HOTREMOVE) to still be able to do memory
hotplug.

However, that broke kexec'ing a kernel on EFI machines because depending
on where the EFI systab was mapped, on at least one machine it isn't
present in the kexec mapping of the second kernel, leading to a triple
fault in the early code.

Fixing this properly requires significantly involved surgery and we
cannot allow ourselves to do that, that close to the merge window.

So disable the RSDP parsing code temporarily until it is fixed properly
in the next release cycle.

Signed-off-by: Borislav Petkov <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Chao Fan <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: Ingo Molnar <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: [email protected]
Cc: Kees Cook <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index c0d6c560df69..5a237e8dbf8d 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -352,7 +352,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	boot_params->hdr.loadflags &= ~KASLR_FLAG;
 
 	/* Save RSDP address for later use. */
-	boot_params->acpi_rsdp_addr = get_rsdp_addr();
+	/* boot_params->acpi_rsdp_addr = get_rsdp_addr(); */
 
 	sanitize_boot_params(boot_params);