[PATCH v2] MdeModulePkg/NvmExpressDxe: fix error status override

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

Commit f6b139b added return status handling to PciIo->Mem.Write.
However, the second status handling will override EFI_DEVICE_ERROR
returned in this branch:

  //
  // Check the NVMe cmd execution result
  //
  if (Status != EFI_TIMEOUT) {
    if ((Cq->Sct == 0) && (Cq->Sc == 0)) {
      Status = EFI_SUCCESS;
    } else {
      Status = EFI_DEVICE_ERROR;
               ^^^^^^^^^^^^^^^^

Since PciIo->Mem.Write will probably return SUCCESS, it causes
NvmExpressPassThru to return SUCCESS even when DEVICE_ERROR occurs.
Callers of NvmExpressPassThru will then continue executing which may
cause further unexpected results, e.g. DiscoverAllNamespaces couldn't
break out the loop.

So we save previous status before calling PciIo->Mem.Write and restore
the previous one if it already contains error.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
---
 MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c b/MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c
index c33038f..7356c1d 100644
--- a/MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c
+++ b/MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c
@@ -453,6 +453,7 @@ NvmExpressPassThru (
 {
   NVME_CONTROLLER_PRIVATE_DATA   *Private;
   EFI_STATUS                     Status;
+  EFI_STATUS                     PreviousStatus;
   EFI_PCI_IO_PROTOCOL            *PciIo;
   NVME_SQ                        *Sq;
   NVME_CQ                        *Cq;
@@ -831,6 +832,7 @@ NvmExpressPassThru (
   }
 
   Data = ReadUnaligned32 ((UINT32*)&Private->CqHdbl[QueueId]);
+  PreviousStatus = Status;
   Status = PciIo->Mem.Write (
                PciIo,
                EfiPciIoWidthUint32,
@@ -839,6 +841,9 @@ NvmExpressPassThru (
                1,
                &Data
                );
+  // The return status of PciIo->Mem.Write should not override
+  // previous status if previous status contains error.
+  Status = EFI_ERROR (PreviousStatus) ? PreviousStatus : Status;
 
   //
   // For now, the code does not support the non-blocking feature for admin queue.
-- 
2.7.2.windows.1