smbios: in case of entry point is 'auto' try to build v2 tables 1st

QEMU for some time now uses SMBIOS 3.0 for PC/Q35 machines by
default, however Windows has a bug in locating SMBIOS 3.0
entrypoint and fails to find tables when booted on SeaBIOS
(on UEFI SMBIOS 3.0 tables work fine since firmware hands
over tables in another way)

Missing SMBIOS tables may lead to some issues for guest
though (worst are: possible reactiveation, inability to
get virtio drivers from 'Windows Update')

It's unclear  at this point if MS will fix the issue on their
side. So instead of it (or rather in addition) this patch
will try to workaround the issue.

aka, use smbios-entry-point-type=auto to make QEMU try
generating conservative SMBIOS 2.0 tables and if that
fails (due to limits/requested configuration) fallback
to SMBIOS 3.0 tables.

With this in place majority of users will use SMBIOS 2.0
tables which work fine with (Windows + legacy BIOS).
The configurations that is not to possible to describe
with SMBIOS 2.0 will switch automatically to SMBIOS 3.0
(which will trigger Windows bug but there is nothing
QEMU can do here, so go and aks Microsoft to real fix).

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Ani Sinha <anisinha@redhat.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Message-Id: <20240314152302.2324164-17-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 49 insertions, 3 deletions

diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
index 48713aa..b046734 100644
--- a/hw/smbios/smbios.c
+++ b/hw/smbios/smbios.c
@@ -1082,7 +1082,7 @@ static void smbios_entry_point_setup(SmbiosEntryPointType ep_type)
     }
 }
 
-void smbios_get_tables(MachineState *ms,
+static bool smbios_get_tables_ep(MachineState *ms,
                        SmbiosEntryPointType ep_type,
                        const struct smbios_phys_mem_area *mem_array,
                        const unsigned int mem_array_size,
@@ -1091,6 +1091,7 @@ void smbios_get_tables(MachineState *ms,
                        Error **errp)
 {
     unsigned i, dimm_cnt, offset;
+    ERRP_GUARD();
 
     assert(ep_type == SMBIOS_ENTRY_POINT_TYPE_32 ||
            ep_type == SMBIOS_ENTRY_POINT_TYPE_64);
@@ -1177,11 +1178,56 @@ void smbios_get_tables(MachineState *ms,
         abort();
     }
 
-    return;
+    return true;
 err_exit:
     g_free(smbios_tables);
     smbios_tables = NULL;
-    return;
+    return false;
+}
+
+void smbios_get_tables(MachineState *ms,
+                       SmbiosEntryPointType ep_type,
+                       const struct smbios_phys_mem_area *mem_array,
+                       const unsigned int mem_array_size,
+                       uint8_t **tables, size_t *tables_len,
+                       uint8_t **anchor, size_t *anchor_len,
+                       Error **errp)
+{
+    Error *local_err = NULL;
+    bool is_valid;
+    ERRP_GUARD();
+
+    switch (ep_type) {
+    case SMBIOS_ENTRY_POINT_TYPE_AUTO:
+    case SMBIOS_ENTRY_POINT_TYPE_32:
+        is_valid = smbios_get_tables_ep(ms, SMBIOS_ENTRY_POINT_TYPE_32,
+                                        mem_array, mem_array_size,
+                                        tables, tables_len,
+                                        anchor, anchor_len,
+                                        &local_err);
+        if (is_valid || ep_type != SMBIOS_ENTRY_POINT_TYPE_AUTO) {
+            break;
+        }
+        /*
+         * fall through in case AUTO endpoint is selected and
+         * SMBIOS 2.x tables can't be generated, to try if SMBIOS 3.x
+         * tables would work
+         */
+    case SMBIOS_ENTRY_POINT_TYPE_64:
+        error_free(local_err);
+        local_err = NULL;
+        is_valid = smbios_get_tables_ep(ms, SMBIOS_ENTRY_POINT_TYPE_64,
+                                        mem_array, mem_array_size,
+                                        tables, tables_len,
+                                        anchor, anchor_len,
+                                        &local_err);
+        break;
+    default:
+        abort();
+    }
+    if (!is_valid) {
+        error_propagate(errp, local_err);
+    }
 }
 
 static void save_opt(const char **dest, QemuOpts *opts, const char *name)