x86/compressed/acpi: Move EFI kexec handling into common code

Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.

In this instance, the current acpi.c kexec handling is mainly used to
get the alternative EFI config table address provided by kexec via a
setup_data entry of type SETUP_EFI. If not present, the code then falls
back to normal EFI config table address provided by EFI system table.
This would need to be done by all call-sites attempting to access the
EFI config table, so just have efi_get_conf_table() handle that
automatically.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-29-brijesh.singh@amd.com

1 files changed, 45 insertions, 1 deletions

diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index 4d363dfc2b33..09fa3b5d70b8 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -78,6 +78,46 @@ unsigned long efi_get_system_table(struct boot_params *bp)
 	return sys_tbl_pa;
 }
 
+/*
+ * EFI config table address changes to virtual address after boot, which may
+ * not be accessible for the kexec'd kernel. To address this, kexec provides
+ * the initial physical address via a struct setup_data entry, which is
+ * checked for here, along with some sanity checks.
+ */
+static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
+						   enum efi_type et)
+{
+#ifdef CONFIG_X86_64
+	struct efi_setup_data *esd = NULL;
+	struct setup_data *data;
+	u64 pa_data;
+
+	pa_data = bp->hdr.setup_data;
+	while (pa_data) {
+		data = (struct setup_data *)pa_data;
+		if (data->type == SETUP_EFI) {
+			esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
+			break;
+		}
+
+		pa_data = data->next;
+	}
+
+	/*
+	 * Original ACPI code falls back to attempting normal EFI boot in these
+	 * cases, so maintain existing behavior by indicating non-kexec
+	 * environment to the caller, but print them for debugging.
+	 */
+	if (esd && !esd->tables) {
+		debug_putstr("kexec EFI environment missing valid configuration table.\n");
+		return NULL;
+	}
+
+	return esd;
+#endif
+	return NULL;
+}
+
 /**
  * efi_get_conf_table - Given a pointer to boot_params, locate and return the physical
  *                      address of EFI configuration table.
@@ -106,8 +146,12 @@ int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
 	et = efi_get_type(bp);
 	if (et == EFI_TYPE_64) {
 		efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa;
+		struct efi_setup_data *esd;
 
-		*cfg_tbl_pa = stbl->tables;
+		/* kexec provides an alternative EFI conf table, check for it. */
+		esd = get_kexec_setup_data(bp, et);
+
+		*cfg_tbl_pa = esd ? esd->tables : stbl->tables;
 		*cfg_tbl_len = stbl->nr_tables;
 	} else if (et == EFI_TYPE_32) {
 		efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa;