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

arch/x86/boot/compressed/acpi.c

@@ -47,57 +47,6 @@ __efi_get_rsdp_addr(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len)
 	return 0;
 }
 
-/* EFI/kexec support is 64-bit only. */
-#ifdef CONFIG_X86_64
-static struct efi_setup_data *get_kexec_setup_data_addr(void)
-{
-	struct setup_data *data;
-	u64 pa_data;
-
-	pa_data = boot_params->hdr.setup_data;
-	while (pa_data) {
-		data = (struct setup_data *)pa_data;
-		if (data->type == SETUP_EFI)
-			return (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
-
-		pa_data = data->next;
-	}
-	return NULL;
-}
-
-static acpi_physical_address kexec_get_rsdp_addr(void)
-{
-	efi_system_table_64_t *systab;
-	struct efi_setup_data *esd;
-	struct efi_info *ei;
-	enum efi_type et;
-
-	esd = (struct efi_setup_data *)get_kexec_setup_data_addr();
-	if (!esd)
-		return 0;
-
-	if (!esd->tables) {
-		debug_putstr("Wrong kexec SETUP_EFI data.\n");
-		return 0;
-	}
-
-	et = efi_get_type(boot_params);
-	if (et != EFI_TYPE_64) {
-		debug_putstr("Unexpected kexec EFI environment (expected 64-bit EFI).\n");
-		return 0;
-	}
-
-	/* Get systab from boot params. */
-	systab = (efi_system_table_64_t *)efi_get_system_table(boot_params);
-	if (!systab)
-		error("EFI system table not found in kexec boot_params.");
-
-	return __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables);
-}
-#else
-static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
-#endif /* CONFIG_X86_64 */
-
 static acpi_physical_address efi_get_rsdp_addr(void)
 {
 #ifdef CONFIG_EFI
@@ -210,14 +159,6 @@ acpi_physical_address get_rsdp_addr(void)
 
 	pa = boot_params->acpi_rsdp_addr;
 
-	/*
-	 * Try to get EFI data from setup_data. This can happen when we're a
-	 * kexec'ed kernel and kexec(1) has passed all the required EFI info to
-	 * us.
-	 */
-	if (!pa)
-		pa = kexec_get_rsdp_addr();
-
 	if (!pa)
 		pa = efi_get_rsdp_addr();
 

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;