[PATCH] OvmfPkg/PvScsiDxe: Fix VS2019 build error because of implicit cast

["Liran Alon" <liran.alon@oracle.com>]

Sean reported that VS2019 build produce the following build error:
INFO - PvScsi.c
INFO - Generating code
INFO - d:\a\1\s\OvmfPkg\PvScsiDxe\PvScsi.c(459): error C2220: the following warning is treated as an error
INFO - d:\a\1\s\OvmfPkg\PvScsiDxe\PvScsi.c(459): warning C4244: '=': conversion from 'const UINT16' to 'UINT8', possible loss of data

This result from an implicit cast from PVSCSI Response->ScsiStatus
(Which is UINT16) to Packet->TargetResponse (Which is UINT8).

Fix this issue by adding an appropriate explicit cast and verify with
assert that this truncation do not result in loss of data.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2651
Reported-by: Sean Brogan <sean.brogan@microsoft.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
---
 OvmfPkg/PvScsiDxe/PvScsi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/PvScsiDxe/PvScsi.c b/OvmfPkg/PvScsiDxe/PvScsi.c
index 0a66c98421a9..1ca50390c0e5 100644
--- a/OvmfPkg/PvScsiDxe/PvScsi.c
+++ b/OvmfPkg/PvScsiDxe/PvScsi.c
@@ -455,8 +455,12 @@ HandleResponse (
 
   //
   // Report target status
+  // (Strangely, PVSCSI interface defines Response->ScsiStatus as UINT16.
+  // But it should de-facto always have a value that fits UINT8. To avoid
+  // unexpected behavior, verify value is in UINT8 bounds before casting)
   //
-  Packet->TargetStatus = Response->ScsiStatus;
+  ASSERT (Response->ScsiStatus <= MAX_UINT8);
+  Packet->TargetStatus = (UINT8)Response->ScsiStatus;
 
   //
   // Host adapter status and function return value depend on
-- 
2.20.1