[PATCH EDK2 v1 1/1] MdeModulePkg/PciBucDxe:Fix issue when initial SR-IVO

["wenyi,xie" <xiewenyi2@huawei.com>]

Reference:https://bugzilla.tianocore.org/show_bug.cgi?id=3804

When calculating SR-IOV reserve bus in function CreatePciIoDevice(),
there are two points may have problem.
LastVF = PFRid + FirstVFOffset + (PciIoDevice->InitialVFs - 1) * VFStride;
PciIoDevice->ReservedBusNum =
(UINT16)(EFI_PCI_BUS_OF_RID (LastVF) - Bus + 1);

The first is that if the value of PciIoDevice->InitialVFs is 0, it will
cause overflow, it's better to check InitialVFs before used.
The second is that if number of bus is not enough for all PF and still
allocate bus for VF, it will lead to PCI enumerating failure.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Wenyi Xie <xiewenyi2@huawei.com>
---
 MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
index 9251388bc268..a4d1db534276 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
@@ -2402,12 +2402,12 @@ CreatePciIoDevice (
       // Calculate LastVF
       //
       PFRid  = EFI_PCI_RID (Bus, Device, Func);
-      LastVF = PFRid + FirstVFOffset + (PciIoDevice->InitialVFs - 1) * VFStride;
+      LastVF = PFRid + FirstVFOffset + (PciIoDevice->InitialVFs == 0 ? 0 : PciIoDevice->InitialVFs - 1) * VFStride;
 
       //
       // Calculate ReservedBusNum for this PF
       //
-      PciIoDevice->ReservedBusNum = (UINT16)(EFI_PCI_BUS_OF_RID (LastVF) - Bus + 1);
+      PciIoDevice->ReservedBusNum = (UINT16)(EFI_PCI_BUS_OF_RID (LastVF) - Bus);
 
       DEBUG ((
         DEBUG_INFO,
-- 
2.20.1.windows.1