[PATCH v6 30/42] x86/compressed/acpi: move EFI vendor table lookup to helper

[Brijesh Singh <brijesh.singh@amd.com>]

From: Michael Roth <michael.roth@amd.com>

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.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/boot/compressed/acpi.c | 50 ++++++++-----------------
 arch/x86/boot/compressed/efi.c  | 65 +++++++++++++++++++++++++++++++++
 arch/x86/boot/compressed/misc.h |  9 +++++
 3 files changed, 90 insertions(+), 34 deletions(-)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index d43ff3ff573b..f2a6092738cd 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -20,46 +20,28 @@
  */
 struct mem_vector immovable_mem[MAX_NUMNODES*2];
 
-/*
- * Search EFI system tables for RSDP.  If both ACPI_20_TABLE_GUID and
- * ACPI_TABLE_GUID are found, take the former, which has more features.
- */
 static acpi_physical_address
-__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
-		    bool efi_64)
+__efi_get_rsdp_addr(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len, bool efi_64)
 {
 	acpi_physical_address rsdp_addr = 0;
 
 #ifdef CONFIG_EFI
-	int i;
-
-	/* Get EFI tables from systab. */
-	for (i = 0; i < nr_tables; i++) {
-		acpi_physical_address table;
-		efi_guid_t guid;
-
-		if (efi_64) {
-			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables + i;
-
-			guid  = tbl->guid;
-			table = tbl->table;
-
-			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
-				debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
-				return 0;
-			}
-		} else {
-			efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables + i;
-
-			guid  = tbl->guid;
-			table = tbl->table;
-		}
+	int ret;
 
-		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
-			rsdp_addr = table;
-		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
-			return table;
-	}
+	/*
+	 * Search EFI system tables for RSDP. Preferred is ACPI_20_TABLE_GUID to
+	 * ACPI_TABLE_GUID because it has more features.
+	 */
+	ret = efi_find_vendor_table(cfg_tbl_pa, cfg_tbl_len, ACPI_20_TABLE_GUID,
+				    efi_64, (unsigned long *)&rsdp_addr);
+	if (!ret)
+		return rsdp_addr;
+
+	/* No ACPI_20_TABLE_GUID found, fallback to ACPI_TABLE_GUID. */
+	ret = efi_find_vendor_table(cfg_tbl_pa, cfg_tbl_len, ACPI_TABLE_GUID,
+				    efi_64, (unsigned long *)&rsdp_addr);
+	if (ret)
+		debug_putstr("Error getting RSDP address.\n");
 #endif
 	return rsdp_addr;
 }
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index e5f39b3f5665..9817e3020207 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -104,3 +104,68 @@ int efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_p
 
 	return 0;
 }
+
+/* Get vendor table address/guid from EFI config table at the given index */
+static int get_vendor_table(void *cfg_tbl, unsigned int idx,
+			    unsigned long *vendor_tbl_pa,
+			    efi_guid_t *vendor_tbl_guid,
+			    bool efi_64)
+{
+	if (efi_64) {
+		efi_config_table_64_t *tbl_entry =
+			(efi_config_table_64_t *)cfg_tbl + idx;
+
+		if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) {
+			debug_putstr("Error: EFI config table entry located above 4GB.\n");
+			return -EINVAL;
+		}
+
+		*vendor_tbl_pa		= tbl_entry->table;
+		*vendor_tbl_guid	= tbl_entry->guid;
+
+	} else {
+		efi_config_table_32_t *tbl_entry =
+			(efi_config_table_32_t *)cfg_tbl + idx;
+
+		*vendor_tbl_pa		= tbl_entry->table;
+		*vendor_tbl_guid	= tbl_entry->guid;
+	}
+
+	return 0;
+}
+
+/**
+ * Given EFI config table, search it for the physical address of the vendor
+ * table associated with GUID.
+ *
+ * @cfg_tbl_pa:        pointer to EFI configuration table
+ * @cfg_tbl_len:       number of entries in EFI configuration table
+ * @guid:              GUID of vendor table
+ * @efi_64:            true if using 64-bit EFI
+ * @vendor_tbl_pa:     location to store physical address of vendor table
+ *
+ * Returns 0 on success. On error, return params are left unchanged.
+ */
+int efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
+			  efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa)
+{
+	unsigned int i;
+
+	for (i = 0; i < cfg_tbl_len; i++) {
+		unsigned long vendor_tbl_pa_tmp;
+		efi_guid_t vendor_tbl_guid;
+		int ret;
+
+		if (get_vendor_table((void *)cfg_tbl_pa, i,
+				     &vendor_tbl_pa_tmp,
+				     &vendor_tbl_guid, efi_64))
+			return -EINVAL;
+
+		if (!efi_guidcmp(guid, vendor_tbl_guid)) {
+			*vendor_tbl_pa = vendor_tbl_pa_tmp;
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index b72fd860362a..d4a26f3d3580 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -181,6 +181,8 @@ int efi_get_system_table(struct boot_params *boot_params,
 			 unsigned long *sys_tbl_pa, bool *is_efi_64);
 int efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
 			unsigned int *cfg_tbl_len, bool *is_efi_64);
+int efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
+			  efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa);
 #else
 static inline int
 efi_get_system_table(struct boot_params *boot_params,
@@ -195,6 +197,13 @@ efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
 {
 	return -ENOENT;
 }
+
+static inline int
+efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
+		      efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa)
+{
+	return -ENOENT;
+}
 #endif /* CONFIG_EFI */
 
 #endif /* BOOT_COMPRESSED_MISC_H */
-- 
2.25.1