smbios: Encode UUID according to SMBIOS specification

Differently from older versions, SMBIOS version 2.6 is explicit about
the encoding of UUID fields:

> Although RFC 4122 recommends network byte order for all fields, the PC
> industry (including the ACPI, UEFI, and Microsoft specifications) has
> consistently used little-endian byte encoding for the first three fields:
> time_low, time_mid, time_hi_and_version. The same encoding, also known as
> wire format, should also be used for the SMBIOS representation of the UUID.
>
> The UUID {00112233-4455-6677-8899-AABBCCDDEEFF} would thus be represented
> as 33 22 11 00 55 44 77 66 88 99 AA BB CC DD EE FF.

The dmidecode tool implements this and decodes the above "wire format"
when SMBIOS version >= 2.6. We moved from SMBIOS version 2.4 to 2.8 when
we started building the SMBIOS entry point inside QEMU, on commit
c97294ec1b9e36887e119589d456557d72ab37b5.

Change smbios_build_type_1_table() to encode the UUID as specified.

To make sure we won't change the guest-visible UUID when upgrading to a
newer QEMU version, keep the old behavior on pc-*-2.1 and older.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/include/hw/i386/smbios.h b/include/hw/i386/smbios.h
index a3f4d88..d2850be 100644
--- a/include/hw/i386/smbios.h
+++ b/include/hw/i386/smbios.h
@@ -20,7 +20,8 @@
 void smbios_entry_add(QemuOpts *opts);
 void smbios_set_cpuid(uint32_t version, uint32_t features);
 void smbios_set_defaults(const char *manufacturer, const char *product,
-                         const char *version, bool legacy_mode);
+                         const char *version, bool legacy_mode,
+                         bool uuid_encoded);
 uint8_t *smbios_get_table_legacy(size_t *length);
 void smbios_get_tables(uint8_t **tables, size_t *tables_len,
                        uint8_t **anchor, size_t *anchor_len);
@@ -72,6 +73,18 @@ struct smbios_type_0 {
     uint8_t embedded_controller_minor_release;
 } QEMU_PACKED;
 
+/* UUID encoding. The time_* fields are little-endian, as specified by SMBIOS
+ * version 2.6.
+ */
+struct smbios_uuid {
+    uint32_t time_low;
+    uint16_t time_mid;
+    uint16_t time_hi_and_version;
+    uint8_t clock_seq_hi_and_reserved;
+    uint8_t clock_seq_low;
+    uint8_t node[6];
+} QEMU_PACKED;
+
 /* SMBIOS type 1 - System Information */
 struct smbios_type_1 {
     struct smbios_structure_header header;
@@ -79,7 +92,7 @@ struct smbios_type_1 {
     uint8_t product_name_str;
     uint8_t version_str;
     uint8_t serial_number_str;
-    uint8_t uuid[16];
+    struct smbios_uuid uuid;
     uint8_t wake_up_type;
     uint8_t sku_number_str;
     uint8_t family_str;