[PATCH] efi/x86-stub: store acpi_rsdp_addr in bootparams

[Dave Young <dyoung@redhat.com>]

Kernel panic occurs during a kexec reboot when EFI runtime services
are not enabled in the first kernel. The issue is that the second
kernel cannot find the ACPI RSDP address during boot.

In legacy boot, the acpi_rsdp_addr is set in early x86 boot code.
However, kernel decompression has moved to the EFI stub for EFI boot.
Therefore, the x86 EFI stub must also be updated to store the
acpi_rsdp_addr in the boot parameters to ensure the kexec kernel
can find it.

(Note: If the pre-kexec kernel was itself a kexec boot, the later kexec
reboot will still utilize the legacy decompressor path, so the original
code remains functional though some cleanups can be done later.)

Signed-off-by: Dave Young <dyoung@redhat.com>
---
 drivers/firmware/efi/libstub/x86-stub.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Index: linux-x86/drivers/firmware/efi/libstub/x86-stub.c
===================================================================
--- linux-x86.orig/drivers/firmware/efi/libstub/x86-stub.c
+++ linux-x86/drivers/firmware/efi/libstub/x86-stub.c
@@ -484,6 +484,22 @@ static void setup_quirks(struct boot_par
 	}
 }
 
+static void setup_acpi_rsdp(struct boot_params *boot_params)
+{
+	u64 rsdp_addr;
+
+	/*
+	 * Search EFI system tables for RSDP. Preferred is ACPI_20_TABLE_GUID to
+	 * ACPI_TABLE_GUID because it has more features.
+	 */
+	rsdp_addr = (u64)get_efi_config_table(ACPI_20_TABLE_GUID);
+	if (!rsdp_addr)
+		rsdp_addr = (u64)get_efi_config_table(ACPI_TABLE_GUID);
+
+	if (rsdp_addr)
+		boot_params->acpi_rsdp_addr = rsdp_addr;
+}
+
 static void setup_graphics(struct boot_params *boot_params)
 {
 	struct screen_info *si = memset(&boot_params->screen_info, 0, sizeof(*si));
@@ -1017,6 +1033,8 @@ void __noreturn efi_stub_entry(efi_handl
 
 	setup_graphics(boot_params);
 
+	setup_acpi_rsdp(boot_params);
+
 	setup_efi_pci(boot_params);
 
 	setup_quirks(boot_params);