OvmfPkg/XenSupport: turn off address decoding before BAR sizing

On Xen, hvmloader firmware leaves address decoding enabled for
enumerated PCI device before jumping into OVMF. OVMF seems to
expect it to be disabled and tries to size PCI BARs in several places
without disabling it which causes BAR64, for example, being
incorrectly placed by QEMU.

Fix it by disabling PCI address decoding explicitly before the
first attempt to size BARs on Xen.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

diff --git a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
index 76fca533c11a9623e98f9b4dc1feac534a57d700..b41bd6b3002bb54105ca93b10f60038fd75af518 100644 (file)
--- a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
+++ b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
@@ -49,6 +49,22 @@ PcatPciRootBridgeBarExisted (
   EnableInterrupts ();\r
 }\r
 \r
+#define PCI_COMMAND_DECODE ((UINT16)(EFI_PCI_COMMAND_IO_SPACE | \\r
+                                     EFI_PCI_COMMAND_MEMORY_SPACE))\r
+STATIC\r
+VOID\r
+PcatPciRootBridgeDecodingDisable (\r
+  IN  UINTN                          Address\r
+  )\r
+{\r
+  UINT16                             Value;\r
+\r
+  Value = PciRead16 (Address);\r
+  if (Value & PCI_COMMAND_DECODE) {\r
+    PciWrite16 (Address, Value & ~(UINT32)PCI_COMMAND_DECODE);\r
+  }\r
+}\r
+\r
 STATIC\r
 VOID\r
 PcatPciRootBridgeParseBars (\r
@@ -75,6 +91,11 @@ PcatPciRootBridgeParseBars (
   UINT64                            Limit;\r
   PCI_ROOT_BRIDGE_APERTURE          *MemAperture;\r
 \r
+  // Disable address decoding for every device before OVMF starts sizing it\r
+  PcatPciRootBridgeDecodingDisable (\r
+    PCI_LIB_ADDRESS (Bus, Device, Function, PCI_COMMAND_OFFSET)\r
+  );\r
+\r
   for (Offset = BarOffsetBase; Offset < BarOffsetEnd; Offset += sizeof (UINT32)) {\r
     PcatPciRootBridgeBarExisted (\r
       PCI_LIB_ADDRESS (Bus, Device, Function, Offset),\r