Ovmf/Xen: add Xen PV console SerialPortLib driver

This implements a SerialPortLib instance that wires up to the
PV console ring used by domU guests. Also imports the required
upstream Xen io/console.h header.

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16976 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c

@@ -0,0 +1,156 @@
+/** @file
+  Xen console SerialPortLib instance
+
+  Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR>
+
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <Base.h>
+#include <Uefi/UefiBaseType.h>
+
+#include <Library/BaseLib.h>
+#include <Library/SerialPortLib.h>
+#include <Library/XenHypercallLib.h>
+
+#include <IndustryStandard/Xen/io/console.h>
+#include <IndustryStandard/Xen/hvm/params.h>
+#include <IndustryStandard/Xen/event_channel.h>
+
+//
+// The code below expects these global variables to be mutable, even in the case
+// that we have been incorporated into SEC or PEIM phase modules (which is
+// allowed by our INF description). While this is a dangerous assumption to make
+// in general, it is actually fine for the Xen domU (guest) environment that
+// this module is intended for, as UEFI always executes from DRAM in that case.
+//
+STATIC evtchn_send_t              mXenConsoleEventChain;
+STATIC struct xencons_interface   *mXenConsoleInterface;
+
+RETURN_STATUS
+EFIAPI
+SerialPortInitialize (
+  VOID
+  )
+{
+  if (!mXenConsoleInterface) {
+    mXenConsoleEventChain.port = (UINT32)XenHypercallHvmGetParam (HVM_PARAM_CONSOLE_EVTCHN);
+    mXenConsoleInterface = (struct xencons_interface *)(UINTN)
+      (XenHypercallHvmGetParam (HVM_PARAM_CONSOLE_PFN) << EFI_PAGE_SHIFT);
+
+    //
+    // No point in ASSERT'ing here as we won't be seeing the output
+    //
+  }
+  return RETURN_SUCCESS;
+}
+
+/**
+  Write data to serial device.
+
+  @param  Buffer           Point of data buffer which need to be written.
+  @param  NumberOfBytes    Number of output bytes which are cached in Buffer.
+
+  @retval 0                Write data failed.
+  @retval !0               Actual number of bytes written to serial device.
+
+**/
+UINTN
+EFIAPI
+SerialPortWrite (
+  IN UINT8     *Buffer,
+  IN UINTN     NumberOfBytes
+  )
+{
+  XENCONS_RING_IDX  Consumer, Producer;
+  UINTN             Sent;
+
+  if (!mXenConsoleInterface) {
+    return 0;
+  }
+
+  Consumer = mXenConsoleInterface->out_cons;
+  Producer = mXenConsoleInterface->out_prod;
+
+  MemoryFence ();
+
+  Sent = 0;
+  while (Sent < NumberOfBytes && ((Producer - Consumer) < sizeof (mXenConsoleInterface->out)))
+    mXenConsoleInterface->out[MASK_XENCONS_IDX(Producer++, mXenConsoleInterface->out)] = Buffer[Sent++];
+
+  MemoryFence ();
+
+  mXenConsoleInterface->out_prod = Producer;
+
+  if (Sent > 0) {
+    XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain);
+  }
+
+  return Sent;
+}
+
+/**
+  Read data from serial device and save the data in buffer.
+
+  @param  Buffer           Point of data buffer which need to be written.
+  @param  NumberOfBytes    Size of Buffer[].
+
+  @retval 0                Read data failed.
+  @retval !0               Actual number of bytes read from serial device.
+
+**/
+UINTN
+EFIAPI
+SerialPortRead (
+  OUT UINT8     *Buffer,
+  IN  UINTN     NumberOfBytes
+)
+{
+  XENCONS_RING_IDX  Consumer, Producer;
+  UINTN             Received;
+
+  if (!mXenConsoleInterface) {
+    return 0;
+  }
+
+  Consumer = mXenConsoleInterface->in_cons;
+  Producer = mXenConsoleInterface->in_prod;
+
+  MemoryFence ();
+
+  Received = 0;
+  while (Received < NumberOfBytes && Consumer < Producer)
+     Buffer[Received++] = mXenConsoleInterface->in[MASK_XENCONS_IDX(Consumer++, mXenConsoleInterface->in)];
+
+  MemoryFence ();
+
+  mXenConsoleInterface->in_cons = Consumer;
+
+  XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain);
+
+  return Received;
+}
+
+/**
+  Check to see if any data is available to be read from the debug device.
+
+  @retval TRUE       At least one byte of data is available to be read
+  @retval FALSE      No data is available to be read
+
+**/
+BOOLEAN
+EFIAPI
+SerialPortPoll (
+  VOID
+  )
+{
+  return mXenConsoleInterface &&
+    mXenConsoleInterface->in_cons != mXenConsoleInterface->in_prod;
+}