[PATCH v6 2/6] OvmfPkg/PciHostBridgeLib: clear PCI aperture vars for (re)init

[Heyi Guo <heyi.guo@linaro.org>]

Use ZeroMem() to initialize (or re-initialize) all fields in temporary
PCI_ROOT_BRIDGE_APERTURE variables to zero. This is not mandatory but
is helpful for future extension: when we add new fields to
PCI_ROOT_BRIDGE_APERTURE and the default value of these fields can
safely be zero, this code will not suffer from an additional
change.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Signed-off-by: Yi Li <phoenix.liyi@huawei.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien.grall@linaro.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---

Notes:
    v6:
    - Move ZeroMem() into the loop [Laszlo]
    - Move ZeroMem() after checking PcdPciDisableBusEnumeration [Laszlo]
    - Commit title change (However 74 characters will cause PatchCheck
      warning, so I tried to reduce the length to eliminate the warning) [laszlo]
    - Minor changes in commit message

 OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c | 4 ++++
 OvmfPkg/Library/PciHostBridgeLib/XenSupport.c       | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
index ff837035caff..65d0ef9252c5 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
+++ b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
@@ -221,6 +221,10 @@ PciHostBridgeGetRootBridges (
     return ScanForRootBridges (Count);
   }
 
+  ZeroMem (&Io, sizeof (Io));
+  ZeroMem (&Mem, sizeof (Mem));
+  ZeroMem (&MemAbove4G, sizeof (MemAbove4G));
+
   Attributes = EFI_PCI_ATTRIBUTE_IDE_PRIMARY_IO |
     EFI_PCI_ATTRIBUTE_IDE_SECONDARY_IO |
     EFI_PCI_ATTRIBUTE_ISA_IO_16 |
diff --git a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
index 31c63ae19e0a..920417950ad9 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
+++ b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
@@ -202,8 +202,13 @@ ScanForRootBridges (
   for (PrimaryBus = 0; PrimaryBus <= PCI_MAX_BUS; PrimaryBus = SubBus + 1) {
     SubBus = PrimaryBus;
     Attributes = 0;
+
+    ZeroMem (&Io, sizeof (Io));
+    ZeroMem (&Mem, sizeof (Mem));
+    ZeroMem (&MemAbove4G, sizeof (MemAbove4G));
+    ZeroMem (&PMem, sizeof (PMem));
+    ZeroMem (&PMemAbove4G, sizeof (PMemAbove4G));
     Io.Base = Mem.Base = MemAbove4G.Base = PMem.Base = PMemAbove4G.Base = MAX_UINT64;
-    Io.Limit = Mem.Limit = MemAbove4G.Limit = PMem.Limit = PMemAbove4G.Limit = 0;
     //
     // Scan all the PCI devices on the primary bus of the PCI root bridge
     //
-- 
2.7.4