[PATCH 3/5] OvmfPkg/VirtioNetDxe: dynamically alloc transmit header

[Brijesh Singh <brijesh.singh@amd.com>]

A network packets are transmitted by placing them into a transmit queue,
each packet is preceded by a VIRTIO_1_0_NET_REQ header. VirtioNetInitTx(),
builds the header once and fills the vring descriptors with the system
physical address of the VIRTIO_1_0_NET_REQ header.

When device is behind the IOMMU, VirtioNet driver is required to provide
the device address of VIRTIO_1_0_NET_REQ header. In this patch we
dynamically allocate the header using AllocateSharedPages() and map with
BusMasterCommonBuffer so that header can be accessed by both processor
and the device.

We could map it with  BusMasterRead but since the header pointer is
used after it was added into vring hence I choose to dynamically allocate
and map it with BusMasterCommonBuffer to avoid the code complexity.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/VirtioNetDxe/VirtioNet.h        |  3 +-
 OvmfPkg/VirtioNetDxe/Events.c           |  6 ++
 OvmfPkg/VirtioNetDxe/SnpInitialize.c    | 65 +++++++++++++++++---
 OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c |  7 +++
 4 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/OvmfPkg/VirtioNetDxe/VirtioNet.h b/OvmfPkg/VirtioNetDxe/VirtioNet.h
index 7df51bd044f5..3efe95a735d8 100644
--- a/OvmfPkg/VirtioNetDxe/VirtioNet.h
+++ b/OvmfPkg/VirtioNetDxe/VirtioNet.h
@@ -94,7 +94,8 @@ typedef struct {
   UINT16                      TxMaxPending;      // VirtioNetInitTx
   UINT16                      TxCurPending;      // VirtioNetInitTx
   UINT16                      *TxFreeStack;      // VirtioNetInitTx
-  VIRTIO_1_0_NET_REQ          TxSharedReq;       // VirtioNetInitTx
+  VIRTIO_1_0_NET_REQ          *TxSharedReq;      // VirtioNetInitTx
+  VOID                        *TxSharedReqMap;   // VirtioMapSharedBuffer
   UINT16                      TxLastUsed;        // VirtioNetInitTx
 } VNET_DEV;
 
diff --git a/OvmfPkg/VirtioNetDxe/Events.c b/OvmfPkg/VirtioNetDxe/Events.c
index 0586a82cdf09..9366aa00a1b3 100644
--- a/OvmfPkg/VirtioNetDxe/Events.c
+++ b/OvmfPkg/VirtioNetDxe/Events.c
@@ -101,4 +101,10 @@ VirtioNetExitBoot (
   // device is reset.
   //
   Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->RxBufMap);
+
+  //
+  // Unmap shared Tx request mapping so that hypervisor will not be able to get
+  // readable data after device is reset.
+  //
+  Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->TxSharedReqMap);
 }
diff --git a/OvmfPkg/VirtioNetDxe/SnpInitialize.c b/OvmfPkg/VirtioNetDxe/SnpInitialize.c
index 6052d40fc6cb..551820e30f36 100644
--- a/OvmfPkg/VirtioNetDxe/SnpInitialize.c
+++ b/OvmfPkg/VirtioNetDxe/SnpInitialize.c
@@ -18,6 +18,7 @@
 **/
 
 #include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 
@@ -151,8 +152,12 @@ VirtioNetInitTx (
   IN OUT VNET_DEV *Dev
   )
 {
-  UINTN TxSharedReqSize;
-  UINTN PktIdx;
+  UINTN                 TxSharedReqSize;
+  UINTN                 PktIdx;
+  EFI_STATUS            Status;
+  EFI_PHYSICAL_ADDRESS  DeviceAddress;
+  UINT64                BufBaseShift;
+  VOID                  *TxSharedReqBuffer;
 
   Dev->TxMaxPending = (UINT16) MIN (Dev->TxRing.QueueSize / 2,
                                  VNET_MAX_PENDING);
@@ -164,24 +169,60 @@ VirtioNetInitTx (
   }
 
   //
+  // Allocate TxSharedReq header and map with BusMasterCommonBuffer so that it
+  // can be accessed equally by both processor and device.
+  //
+  Status = Dev->VirtIo->AllocateSharedPages (
+                          Dev->VirtIo,
+                          EFI_SIZE_TO_PAGES (sizeof *(Dev->TxSharedReq)),
+                          &TxSharedReqBuffer
+                          );
+  if (EFI_ERROR (Status)) {
+    return EFI_OUT_OF_RESOURCES;
+  }
+
+  Status = VirtioMapAllBytesInSharedBuffer (
+             Dev->VirtIo,
+             VirtioOperationBusMasterCommonBuffer,
+             TxSharedReqBuffer,
+             sizeof *(Dev->TxSharedReq),
+             &DeviceAddress,
+             &Dev->TxSharedReqMap
+             );
+  if (EFI_ERROR (Status)) {
+    Status = EFI_OUT_OF_RESOURCES;
+    goto FreeBuffer;
+  }
+
+  Dev->TxSharedReq = TxSharedReqBuffer;
+
+  BufBaseShift = (UINT64) (UINTN)Dev->TxSharedReq - (UINT64) DeviceAddress;
+
+  ZeroMem ((VOID *) Dev->TxSharedReq, sizeof *(Dev->TxSharedReq));
+
+  //
   // In VirtIo 1.0, the NumBuffers field is mandatory. In 0.9.5, it depends on
   // VIRTIO_NET_F_MRG_RXBUF, which we never negotiate.
   //
   TxSharedReqSize = (Dev->VirtIo->Revision < VIRTIO_SPEC_REVISION (1, 0, 0)) ?
-                    sizeof Dev->TxSharedReq.V0_9_5 :
-                    sizeof Dev->TxSharedReq;
+                    sizeof ((Dev->TxSharedReq)->V0_9_5) :
+                    sizeof *(Dev->TxSharedReq);
 
   for (PktIdx = 0; PktIdx < Dev->TxMaxPending; ++PktIdx) {
     UINT16 DescIdx;
+    UINT64 Address;
 
     DescIdx = (UINT16) (2 * PktIdx);
     Dev->TxFreeStack[PktIdx] = DescIdx;
 
+    Address = (UINTN) Dev->TxSharedReq;
+    Address += BufBaseShift;
+
     //
     // For each possibly pending packet, lay out the descriptor for the common
     // (unmodified by the host) virtio-net request header.
     //
-    Dev->TxRing.Desc[DescIdx].Addr  = (UINTN) &Dev->TxSharedReq;
+    Dev->TxRing.Desc[DescIdx].Addr  = Address;
     Dev->TxRing.Desc[DescIdx].Len   = (UINT32) TxSharedReqSize;
     Dev->TxRing.Desc[DescIdx].Flags = VRING_DESC_F_NEXT;
     Dev->TxRing.Desc[DescIdx].Next  = (UINT16) (DescIdx + 1);
@@ -196,13 +237,13 @@ VirtioNetInitTx (
   //
   // virtio-0.9.5, Appendix C, Packet Transmission
   //
-  Dev->TxSharedReq.V0_9_5.Flags   = 0;
-  Dev->TxSharedReq.V0_9_5.GsoType = VIRTIO_NET_HDR_GSO_NONE;
+  Dev->TxSharedReq->V0_9_5.Flags   = 0;
+  Dev->TxSharedReq->V0_9_5.GsoType = VIRTIO_NET_HDR_GSO_NONE;
 
   //
   // For VirtIo 1.0 only -- the field exists, but it is unused
   //
-  Dev->TxSharedReq.NumBuffers = 0;
+  Dev->TxSharedReq->NumBuffers = 0;
 
   //
   // virtio-0.9.5, 2.4.2 Receiving Used Buffers From the Device
@@ -217,6 +258,14 @@ VirtioNetInitTx (
   *Dev->TxRing.Avail.Flags = (UINT16) VRING_AVAIL_F_NO_INTERRUPT;
 
   return EFI_SUCCESS;
+
+FreeBuffer:
+  Dev->VirtIo->FreeSharedPages (
+                 Dev->VirtIo,
+                 EFI_SIZE_TO_PAGES (sizeof *(Dev->TxSharedReq)),
+                 (VOID *) Dev->TxSharedReq
+                 );
+  return Status;
 }
 
 
diff --git a/OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c b/OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c
index 4c9d9ece0790..aeb9e6605f0d 100644
--- a/OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c
+++ b/OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c
@@ -54,5 +54,12 @@ VirtioNetShutdownTx (
   IN OUT VNET_DEV *Dev
   )
 {
+  Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->TxSharedReqMap);
+  Dev->VirtIo->FreeSharedPages (
+                 Dev->VirtIo,
+                 EFI_SIZE_TO_PAGES (sizeof *(Dev->TxSharedReq)),
+                 (VOID *) Dev->TxSharedReq
+                 );
+
   FreePool (Dev->TxFreeStack);
 }
-- 
2.7.4