[PATCH 6.18 735/752] x86/kexec: Copy ACPI root pointer address from config table

Sasha Levin
2026-02-28T17:59:11Z

From: Ard Biesheuvel <ardb@kernel.org>

[ Upstream commit e00ac9e5afb5d80c0168ec88d8e8662a54af8249 ]

Dave reports that kexec may fail when the first kernel boots via the EFI
stub but without EFI runtime services, as in that case, the RSDP address
field in struct bootparams is never assigned. Kexec copies this value
into the version of struct bootparams that it provides to the incoming
kernel, which may have no other means to locate the ACPI root pointer.

So take the value from the EFI config tables if no root pointer has been
set in the first kernel's struct bootparams.

Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1
Reported-by: Dave Young <dyoung@redhat.com>
Tested-by: Dave Young <dyoung@redhat.com>
Link: https://lore.kernel.org/linux-efi/aZQg_tRQmdKNadCg@darkstar.users.ipa.redhat.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/kexec-bzimage64.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index c3244ac680d14..f3b451eb49be1 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -192,6 +192,13 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
struct efi_info *current_ei = &boot_params.efi_info;
struct efi_info *ei = &params->efi_info;

+ if (!params->acpi_rsdp_addr) {
+ if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
+ params->acpi_rsdp_addr = efi.acpi20;
+ else if (efi.acpi != EFI_INVALID_TABLE_ADDR)
+ params->acpi_rsdp_addr = efi.acpi;
+ }
+
if (!efi_enabled(EFI_RUNTIME_SERVICES))
return 0;

--
2.51.0