From: Liran Alon <liran.alon@oracle.com>
Date: Sat, 28 Mar 2020 20:00:57 +0000 (+0300)
Subject: OvmfPkg/PvScsiDxe: Introduce DMA communication buffer
X-Git-Tag: edk2-stable202005~246
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=6510e1979491d28c82944e0cfdab5713d482efa1

OvmfPkg/PvScsiDxe: Introduce DMA communication buffer

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
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Message-Id: <20200328200100.60786-15-liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---

diff --git a/OvmfPkg/PvScsiDxe/PvScsi.c b/OvmfPkg/PvScsiDxe/PvScsi.c
index c7d367e83a..6e350bb2d6 100644
--- a/OvmfPkg/PvScsiDxe/PvScsi.c
+++ b/OvmfPkg/PvScsiDxe/PvScsi.c
@@ -677,6 +677,19 @@ PvScsiInit (
     goto RestorePciAttributes;
   }
 
+  //
+  // Allocate DMA communication buffer
+  //
+  Status = PvScsiAllocateSharedPages (
+             Dev,
+             EFI_SIZE_TO_PAGES (sizeof (*Dev->DmaBuf)),
+             (VOID **)&Dev->DmaBuf,
+             &Dev->DmaBufDmaDesc
+             );
+  if (EFI_ERROR (Status)) {
+    goto FreeRings;
+  }
+
   //
   // Populate the exported interface's attributes
   //
@@ -708,6 +721,15 @@ PvScsiInit (
 
   return EFI_SUCCESS;
 
+FreeRings:
+  //
+  // Reset device to stop device usage of the rings.
+  // This is required to safely free the rings.
+  //
+  PvScsiResetAdapter (Dev);
+
+  PvScsiFreeRings (Dev);
+
 RestorePciAttributes:
   PvScsiRestorePciAttributes (Dev);
 
@@ -721,11 +743,25 @@ PvScsiUninit (
   )
 {
   //
-  // Reset device to stop device usage of the rings.
-  // This is required to safely free the rings.
+  // Reset device to:
+  // - Make device stop processing all requests.
+  // - Stop device usage of the rings.
+  //
+  // This is required to safely free the DMA communication buffer
+  // and the rings.
   //
   PvScsiResetAdapter (Dev);
 
+  //
+  // Free DMA communication buffer
+  //
+  PvScsiFreeSharedPages (
+    Dev,
+    EFI_SIZE_TO_PAGES (sizeof (*Dev->DmaBuf)),
+    Dev->DmaBuf,
+    &Dev->DmaBufDmaDesc
+    );
+
   PvScsiFreeRings (Dev);
 
   PvScsiRestorePciAttributes (Dev);
diff --git a/OvmfPkg/PvScsiDxe/PvScsi.h b/OvmfPkg/PvScsiDxe/PvScsi.h
index 6d23b6e1ec..fff12146dc 100644
--- a/OvmfPkg/PvScsiDxe/PvScsi.h
+++ b/OvmfPkg/PvScsiDxe/PvScsi.h
@@ -31,6 +31,21 @@ typedef struct {
   PVSCSI_DMA_DESC      RingCmpsDmaDesc;
 } PVSCSI_RING_DESC;
 
+typedef struct {
+  //
+  // As EFI_EXT_SCSI_PASS_THRU_SCSI_REQUEST_PACKET.SenseDataLength is defined
+  // as UINT8, defining here SenseData size to MAX_UINT8 will guarantee it
+  // cannot overflow when passed to device.
+  //
+  UINT8     SenseData[MAX_UINT8];
+  //
+  // This size of the data is arbitrarily chosen.
+  // It seems to be sufficient for all I/O requests sent through
+  // EFI_SCSI_PASS_THRU_PROTOCOL.PassThru() for common boot scenarios.
+  //
+  UINT8     Data[0x2000];
+} PVSCSI_DMA_BUFFER;
+
 #define PVSCSI_SIG SIGNATURE_32 ('P', 'S', 'C', 'S')
 
 typedef struct {
@@ -38,6 +53,8 @@ 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 +64,7 @@ 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_