x86/CPU/AMD: Print AGESA string from DMI additional information entry

Type 40 entries (Additional Information) are summarized in section 7.41 as
part of the SMBIOS specification.  Generally, these entries aren't interesting
to save.

However on some AMD Zen systems, the AGESA version is stored here. This is
useful to save to the kernel message logs for debugging. It can be used to
cross-reference issues.

Implement an iterator for the Additional Information entries. Use this to find
and print the AGESA string. Do so in AMD code, since the use case is
AMD-specific.

  [ bp: Match only "AGESA". ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Co-developed-by: "Mario Limonciello (AMD)" <superm1@kernel.org>
Signed-off-by: "Mario Limonciello (AMD)" <superm1@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Link: https://patch.msgid.link/20260307141024.819807-6-superm1@kernel.org

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 09de584e4c8fa951a01137acbdb95e61a42db903..33b740c26bef1b73ff8b06278c3479d876887f6e 100644 (file)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/export.h>
 #include <linux/bitops.h>
+#include <linux/dmi.h>
 #include <linux/elf.h>
 #include <linux/mm.h>
 #include <linux/kvm_types.h>
@@ -1380,3 +1381,51 @@ static __init int print_s5_reset_status_mmio(void)
        return 0;
 }
 late_initcall(print_s5_reset_status_mmio);
+
+static void __init dmi_scan_additional(const struct dmi_header *d, void *p)
+{
+       struct dmi_a_info *info = (struct dmi_a_info *)d;
+       void *next, *end;
+
+       if (!IS_ENABLED(CONFIG_DMI))
+               return;
+
+       if (info->header.type != DMI_ENTRY_ADDITIONAL ||
+           info->header.length < DMI_A_INFO_MIN_SIZE ||
+           info->count < 1)
+               return;
+
+       next = (void *)(info + 1);
+       end  = (void *)info + info->header.length;
+
+       do {
+               struct dmi_a_info_entry *entry;
+               const char *string_ptr;
+
+               entry = (struct dmi_a_info_entry *)next;
+
+               /*
+                * Not much can be done to validate data. At least the entry
+                * length shouldn't be 0.
+                */
+               if (!entry->length)
+                       return;
+
+               string_ptr = dmi_string_nosave(&info->header, entry->str_num);
+
+               /* Sample string: AGESA!V9 StrixKrackanPI-FP8 1.1.0.0c */
+               if (!strncmp(string_ptr, "AGESA", 5)) {
+                       pr_info("AGESA: %s\n", string_ptr);
+                       break;
+               }
+
+               next += entry->length;
+       } while (end - next >= DMI_A_INFO_ENT_MIN_SIZE);
+}
+
+static __init int print_dmi_agesa(void)
+{
+       dmi_walk(dmi_scan_additional, NULL);
+       return 0;
+}
+late_initcall(print_dmi_agesa);

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index ed6235ac576b6c3a6974b21d7beada87336c45a0..a3f7dabd49554d0ca0ced819bd62299e996c15de 100644 (file)
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -47,7 +47,7 @@ static struct dmi_memdev_info {
 static int dmi_memdev_nr;
 static int dmi_memdev_populated_nr __initdata;
 
-static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
+const char *dmi_string_nosave(const struct dmi_header *dm, u8 s)
 {
        const u8 *bp = ((u8 *) dm) + dm->length;
        const u8 *nsp;
@@ -66,6 +66,7 @@ static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
 
        return dmi_empty_string;
 }
+EXPORT_SYMBOL_GPL(dmi_string_nosave);
 
 static const char * __init dmi_string(const struct dmi_header *dm, u8 s)
 {

diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index 2eedf44e680126bb079186235d1916564cf8d6f7..c8700e6a694d1725905a8dd8b0950681e14a968e 100644 (file)
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -91,6 +91,21 @@ struct dmi_device {
        void *device_data;      /* Type specific data */
 };
 
+#define DMI_A_INFO_ENT_MIN_SIZE 0x6
+struct dmi_a_info_entry {
+       u8 length;
+       u16 handle;
+       u8 offset;
+       u8 str_num;
+       u8 value[];
+} __packed;
+
+#define DMI_A_INFO_MIN_SIZE    0xB
+struct dmi_a_info {
+       struct dmi_header header;
+       u8 count;
+} __packed;
+
 #ifdef CONFIG_DMI
 
 struct dmi_dev_onboard {
@@ -120,6 +135,7 @@ extern void dmi_memdev_name(u16 handle, const char **bank, const char **device);
 extern u64 dmi_memdev_size(u16 handle);
 extern u8 dmi_memdev_type(u16 handle);
 extern u16 dmi_memdev_handle(int slot);
+const char *dmi_string_nosave(const struct dmi_header *dm, u8 s);
 
 #else
 
@@ -153,6 +169,8 @@ static inline u8 dmi_memdev_type(u16 handle) { return 0x0; }
 static inline u16 dmi_memdev_handle(int slot) { return 0xffff; }
 static inline const struct dmi_system_id *
        dmi_first_match(const struct dmi_system_id *list) { return NULL; }
+static inline const char *
+       dmi_string_nosave(const struct dmi_header *dm, u8 s) { return ""; }
 
 #endif