[PATCH v2 2/5] OvmfPkg/Microvm/fdt: load fdt from fw_cfg

["Gerd Hoffmann" <kraxel@redhat.com>]

Needed for hardware detection: virtio-mmio devices for now,
later also pcie root bridge.

Depends on patched qemu which actually provides an fdt:
https://gitlab.com/kraxel/qemu/-/commits/sirius/microvm-device-tree

https://bugzilla.tianocore.org/show_bug.cgi?id=3689
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/PlatformPei/PlatformPei.inf |  1 +
 OvmfPkg/PlatformPei/Platform.c      | 40 +++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 67eb7aa7166b..56876184b17a 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -44,6 +44,7 @@ [Packages]
 
 [Guids]
   gEfiMemoryTypeInformationGuid
+  gFdtHobGuid
 
 [LibraryClasses]
   BaseLib
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index df2d9ad015aa..3c0cdba67c83 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -321,6 +321,45 @@ PciExBarInitialization (
     );
 }
 
+VOID
+MicrovmInitialization (
+  VOID
+  )
+{
+    FIRMWARE_CONFIG_ITEM FdtItem;
+    UINTN FdtSize;
+    UINTN FdtPages;
+    EFI_STATUS Status;
+    UINT64 *FdtHobData;
+    VOID *NewBase;
+
+    Status = QemuFwCfgFindFile ("etc/fdt", &FdtItem, &FdtSize);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_INFO, "%a: no etc/fdt found in fw_cfg\n", __FUNCTION__));
+      return;
+    }
+
+    FdtPages = EFI_SIZE_TO_PAGES (FdtSize);
+    NewBase = AllocatePages (FdtPages);
+    if (NewBase == NULL) {
+      DEBUG ((DEBUG_INFO, "%a: AllocatePages failed\n", __FUNCTION__));
+      return;
+    }
+
+    QemuFwCfgSelectItem (FdtItem);
+    QemuFwCfgReadBytes (FdtSize, NewBase);
+
+    FdtHobData = BuildGuidHob (&gFdtHobGuid, sizeof (*FdtHobData));
+    if (FdtHobData == NULL) {
+      DEBUG ((DEBUG_INFO, "%a: BuildGuidHob failed\n", __FUNCTION__));
+      return;
+    }
+
+    DEBUG ((DEBUG_INFO, "%a: fdt at 0x%x (size %d)\n", __FUNCTION__,
+            NewBase, FdtSize));
+    *FdtHobData = (UINTN)NewBase;
+}
+
 VOID
 MiscInitialization (
   VOID
@@ -368,6 +407,7 @@ MiscInitialization (
       break;
     case 0xffff: /* microvm */
       DEBUG ((DEBUG_INFO, "%a: microvm\n", __FUNCTION__));
+      MicrovmInitialization();
       PcdStatus = PcdSet16S (PcdOvmfHostBridgePciDevId,
                              MICROVM_PSEUDO_DEVICE_ID);
       ASSERT_RETURN_ERROR (PcdStatus);
-- 
2.31.1