Re: [PATCH v1 17/21] Ovmf/Xen: add Xen PV console SerialPortLib driver

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

On Fri, 23 Jan 2015, Ard Biesheuvel wrote:
> On 23 January 2015 at 18:54, Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
> > On Fri, 23 Jan 2015, Ard Biesheuvel wrote:
> >> 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
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> ---
> >>  OvmfPkg/Include/IndustryStandard/Xen/io/console.h  |  51 +++++++
> >>  .../XenConsoleSerialPortLib.c                      | 147 +++++++++++++++++++++
> >>  .../XenConsoleSerialPortLib.inf                    |  34 +++++
> >>  3 files changed, 232 insertions(+)
> >>  create mode 100644 OvmfPkg/Include/IndustryStandard/Xen/io/console.h
> >>  create mode 100644 OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
> >>  create mode 100644 OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf
> >>
> >> diff --git a/OvmfPkg/Include/IndustryStandard/Xen/io/console.h b/OvmfPkg/Include/IndustryStandard/Xen/io/console.h
> >> new file mode 100644
> >> index 000000000000..f1caa9765bcf
> >> --- /dev/null
> >> +++ b/OvmfPkg/Include/IndustryStandard/Xen/io/console.h
> >> @@ -0,0 +1,51 @@
> >> +/******************************************************************************
> >> + * console.h
> >> + *
> >> + * Console I/O interface for Xen guest OSes.
> >> + *
> >> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> >> + * of this software and associated documentation files (the "Software"), to
> >> + * deal in the Software without restriction, including without limitation the
> >> + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> >> + * sell copies of the Software, and to permit persons to whom the Software is
> >> + * furnished to do so, subject to the following conditions:
> >> + *
> >> + * The above copyright notice and this permission notice shall be included in
> >> + * all copies or substantial portions of the Software.
> >> + *
> >> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> >> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> >> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> >> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> >> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> >> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> >> + * DEALINGS IN THE SOFTWARE.
> >> + *
> >> + * Copyright (c) 2005, Keir Fraser
> >> + */
> >> +
> >> +#ifndef __XEN_PUBLIC_IO_CONSOLE_H__
> >> +#define __XEN_PUBLIC_IO_CONSOLE_H__
> >> +
> >> +typedef UINT32 XENCONS_RING_IDX;
> >> +
> >> +#define MASK_XENCONS_IDX(idx, ring) ((idx) & (sizeof(ring)-1))
> >> +
> >> +struct xencons_interface {
> >> +    char in[1024];
> >> +    char out[2048];
> >> +    XENCONS_RING_IDX in_cons, in_prod;
> >> +    XENCONS_RING_IDX out_cons, out_prod;
> >> +};
> >> +
> >> +#endif /* __XEN_PUBLIC_IO_CONSOLE_H__ */
> >> +
> >> +/*
> >> + * Local variables:
> >> + * mode: C
> >> + * c-file-style: "BSD"
> >> + * c-basic-offset: 4
> >> + * tab-width: 4
> >> + * indent-tabs-mode: nil
> >> + * End:
> >> + */
> >> diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
> >> new file mode 100644
> >> index 000000000000..97344dc4efb0
> >> --- /dev/null
> >> +++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
> >> @@ -0,0 +1,147 @@
> >> +/** @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>
> >> +
> >> +STATIC evtchn_send_t              mXenConsoleEventChain;
> >> +STATIC struct xencons_interface   *mXenConsoleInterface;
> >> +
> >> +RETURN_STATUS
> >> +EFIAPI
> >> +SerialPortInitialize (
> >> +  VOID
> >> +  )
> >> +{
> >> +  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;
> >
> > Do you need a memory barrier after reading in_cons and in_prod and
> > before comparing them, to make sure that the view is consistent?
> >
> 
> I don't think so. The memory reads both have to complete before the
> comparison can be performed, and the comparison itself is not a memory
> access.

I think that you are right


> >
> >> +}
> >> diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf
> >> new file mode 100644
> >> index 000000000000..f7925b3e6bc3
> >> --- /dev/null
> >> +++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf
> >> @@ -0,0 +1,34 @@
> >> +#/** @file
> >> +#
> >> +#  Component description file for XenConsoleSerialPortLib module
> >> +#
> >> +#  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.
> >> +#
> >> +#**/
> >> +
> >> +[Defines]
> >> +  INF_VERSION                    = 0x00010005
> >> +  BASE_NAME                      = XenConsoleSerialPortLib
> >> +  FILE_GUID                      = 401406DD-BCAC-4B91-9F4E-72A7FEBE4762
> >> +  MODULE_TYPE                    = BASE
> >> +  VERSION_STRING                 = 1.0
> >> +  LIBRARY_CLASS                  = SerialPortLib
> >> +
> >> +[Sources.common]
> >> +  XenConsoleSerialPortLib.c
> >> +
> >> +[LibraryClasses]
> >> +  BaseLib
> >> +  XenHypercallLib
> >> +
> >> +[Packages]
> >> +  MdePkg/MdePkg.dec
> >> +  OvmfPkg/OvmfPkg.dec
> >> --
> >> 1.8.3.2
> >>
>