[PATCH 14/17] OvmfPkg/PvScsiDxe: Introduce DMA communication buffer

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

In case device is constrained by IOMMU or guest is running under AMD SEV,
input/output buffers provided to device (DataBuffer and SenseData) needs
to be explicitly mapped to device by PciIo->Map().

To avoid the overhead of mapping/unmapping the DataBuffer and SenseData
to the device for every SCSI requst (And to simplify code), introduce a
single DMA communication buffer that will be mapped to device on
initialization. When a SCSI request needs to be sent to device, the
DataBuffer and SenseData will be copied from/to the DMA communication
buffer as required. This will be done by the following commits.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2567
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
---
 OvmfPkg/PvScsiDxe/PvScsi.c | 24 ++++++++++++++++++++++++
 OvmfPkg/PvScsiDxe/PvScsi.h | 10 ++++++++++
 2 files changed, 34 insertions(+)

diff --git a/OvmfPkg/PvScsiDxe/PvScsi.c b/OvmfPkg/PvScsiDxe/PvScsi.c
index c3f5d38f3d30..e48929bf044c 100644
--- a/OvmfPkg/PvScsiDxe/PvScsi.c
+++ b/OvmfPkg/PvScsiDxe/PvScsi.c
@@ -638,6 +638,20 @@ PvScsiInit (
     return Status;
   }
 
+  //
+  // Allocate DMA communication buffer
+  //
+  Status = PvScsiAllocateSharedPages (
+             Dev,
+             EFI_SIZE_TO_PAGES (sizeof (*Dev->DmaBuf)),
+             EfiPciIoOperationBusMasterCommonBuffer,
+             (VOID **)&Dev->DmaBuf,
+             &Dev->DmaBufDmaDesc
+             );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
   //
   // Populate the exported interface's attributes
   //
@@ -676,6 +690,16 @@ PvScsiUninit (
   IN OUT PVSCSI_DEV *Dev
   )
 {
+  //
+  // Free DMA communication buffer
+  //
+  PvScsiFreeSharedPages (
+    Dev,
+    EFI_SIZE_TO_PAGES (sizeof (*Dev->DmaBuf)),
+    (VOID **)&Dev->DmaBuf,
+    &Dev->DmaBufDmaDesc
+    );
+
   //
   // Free PVSCSI rings
   //
diff --git a/OvmfPkg/PvScsiDxe/PvScsi.h b/OvmfPkg/PvScsiDxe/PvScsi.h
index 6d23b6e1eccf..7f91d70fec79 100644
--- a/OvmfPkg/PvScsiDxe/PvScsi.h
+++ b/OvmfPkg/PvScsiDxe/PvScsi.h
@@ -31,6 +31,11 @@ typedef struct {
   PVSCSI_DMA_DESC      RingCmpsDmaDesc;
 } PVSCSI_RING_DESC;
 
+typedef struct {
+  UINT8     SenseData[MAX_UINT8];
+  UINT8     Data[0x2000];
+} PVSCSI_DMA_BUFFER;
+
 #define PVSCSI_SIG SIGNATURE_32 ('P', 'S', 'C', 'S')
 
 typedef struct {
@@ -38,6 +43,8 @@ typedef struct {
   EFI_PCI_IO_PROTOCOL             *PciIo;
   UINT64                          OriginalPciAttributes;
   PVSCSI_RING_DESC                RingDesc;
+  PVSCSI_DMA_BUFFER               *DmaBuf;
+  PVSCSI_DMA_DESC                 DmaBufDmaDesc;
   UINT8                           MaxTarget;
   UINT8                           MaxLun;
   EFI_EXT_SCSI_PASS_THRU_PROTOCOL PassThru;
@@ -47,4 +54,7 @@ typedef struct {
 #define PVSCSI_FROM_PASS_THRU(PassThruPointer) \
   CR (PassThruPointer, PVSCSI_DEV, PassThru, PVSCSI_SIG)
 
+#define PVSCSI_DMA_BUF_DEV_ADDR(Dev, MemberName) \
+  (Dev->DmaBufDmaDesc.DeviceAddress + OFFSET_OF(PVSCSI_DMA_BUFFER, MemberName))
+
 #endif // __PVSCSI_DXE_H_
-- 
2.20.1