[PATCH] hvmloader: Update to SMBIOS 2.6

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Currently, hvmloader uses SMBIOS 2.4, however, when using OVMF, the
SMBIOS is patched to 2.8, which has clarified the UUID format (as GUID).

In Linux, if the SMBIOS version is >= 2.6, the GUID format is used, else
(undefined as per SMBIOS spec), big endian is used (used by Xen). Therefore,
you have a endian mismatch causing the UUIDs to mismatch in the guest.

$ cat /sys/hypervisor/uuid
e865e63f-3d30-4f0b-83e0-8fdfc1e30eb7
$ cat /sys/devices/virtual/dmi/id/product_uuid
3fe665e8-303d-0b4f-83e0-8fdfc1e30eb7
$ cat /sys/devices/virtual/dmi/id/product_serial
e865e63f-3d30-4f0b-83e0-8fdfc1e30eb7

This patch updates the SMBIOS version from 2.4 to 2.6 and fixup the UUID
written in the table; which effectively fix this endianness mismatch with
OVMF; while the UUID displayed by Linux is still the same for SeaBIOS.

Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
This effectively changes the UUID seen with UEFI guests as it was
actually inconsistent with SeaBIOS and SMBIOS expectations.
---
 tools/firmware/hvmloader/smbios.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/tools/firmware/hvmloader/smbios.c 
b/tools/firmware/hvmloader/smbios.c
index 6bcdcc233a..f4822ae6f8 100644
--- a/tools/firmware/hvmloader/smbios.c
+++ b/tools/firmware/hvmloader/smbios.c
@@ -352,7 +352,7 @@ smbios_entry_point_init(void *start,
     memcpy(ep->anchor_string, "_SM_", 4);
     ep->length = 0x1f;
     ep->smbios_major_version = 2;
-    ep->smbios_minor_version = 4;
+    ep->smbios_minor_version = 6;
     ep->max_structure_size = max_structure_size;
     ep->entry_point_revision = 0;
     memcpy(ep->intermediate_anchor_string, "_DMI_", 5);
@@ -462,7 +462,23 @@ smbios_type_1_init(void *start, const char *xen_version,
     p->version_str = 3;
     p->serial_number_str = 4;
 
-    memcpy(p->uuid, uuid, 16);
+    /*
+     * Xen uses OSF DCE UUIDs which is fully big endian, however,
+     * GUIDs (which requirement is clarified by SMBIOS >= 2.6) has the
+     * first 3 components appearing as being little endian and the rest
+     * as still being big endian.
+     */
+    /* First component */
+    for ( unsigned int i = 0; i < 4; i++ )
+        p->uuid[i] = uuid[4 - i - 1];
+    /* Second component */
+    p->uuid[4] = uuid[5];
+    p->uuid[5] = uuid[4];
+    /* Third component */
+    p->uuid[6] = uuid[7];
+    p->uuid[7] = uuid[6];
+    /* Rest */
+    memcpy(p->uuid + 8, uuid + 8, 8);
 
     p->wake_up_type = 0x06; /* power switch */
     p->sku_str = 0;
-- 
2.50.1



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