diff --git a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
index affb6ffd88..346a5aed94 100644
--- a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
+++ b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
@@ -41,6 +41,12 @@
[Sources.Ia32, Sources.X64]
VbeShim.c
+ UnalignedIoGcc.c | GCC
+ UnalignedIoMsc.c | MSFT
+ UnalignedIoIcc.c | INTEL
+
+[Sources.IPF, Sources.EBC, Sources.ARM, Sources.AARCH64]
+ UnalignedIoUnsupported.c
[Packages]
MdePkg/MdePkg.dec
diff --git a/OvmfPkg/QemuVideoDxe/UnalignedIoGcc.c b/OvmfPkg/QemuVideoDxe/UnalignedIoGcc.c
new file mode 100644
index 0000000000..105d55d3b9
--- /dev/null
+++ b/OvmfPkg/QemuVideoDxe/UnalignedIoGcc.c
@@ -0,0 +1,70 @@
+/** @file
+ Unaligned Port I/O. This file has compiler specifics for GCC as there is no
+ ANSI C standard for doing IO.
+
+ Based on IoLibGcc.c.
+
+ Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.
+ 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 "UnalignedIoInternal.h"
+
+/**
+ Performs a 32-bit write to the specified, possibly unaligned I/O-type
+ address.
+
+ Writes the 32-bit I/O port specified by Port with the value specified by
+ Value and returns Value. This function must guarantee that all I/O read and
+ write operations are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port I/O port address
+ @param[in] Value 32-bit word to write
+
+ @return The value written to the I/O port.
+
+**/
+UINT32
+UnalignedIoWrite32 (
+ IN UINTN Port,
+ IN UINT32 Value
+ )
+{
+ __asm__ __volatile__ ( "outl %0, %1" : : "a" (Value), "d" ((UINT16)Port) );
+ return Value;
+}
+
+/**
+ Reads a 32-bit word from the specified, possibly unaligned I/O-type address.
+
+ Reads the 32-bit I/O port specified by Port. The 32-bit read value is
+ returned. This function must guarantee that all I/O read and write operations
+ are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port The I/O port to read.
+
+ @return The value read.
+
+**/
+UINT32
+UnalignedIoRead32 (
+ IN UINTN Port
+ )
+{
+ UINT32 Data;
+ __asm__ __volatile__ ( "inl %1, %0" : "=a" (Data) : "d" ((UINT16)Port) );
+ return Data;
+}
+
diff --git a/OvmfPkg/QemuVideoDxe/UnalignedIoIcc.c b/OvmfPkg/QemuVideoDxe/UnalignedIoIcc.c
new file mode 100644
index 0000000000..79f3e446dd
--- /dev/null
+++ b/OvmfPkg/QemuVideoDxe/UnalignedIoIcc.c
@@ -0,0 +1,80 @@
+/** @file
+ Unaligned port I/O. This file has compiler specifics for ICC as there
+ is no ANSI C standard for doing IO.
+
+ Based on IoLibIcc.c.
+
+ Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.
+ 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 "UnalignedIoInternal.h"
+
+/**
+ Performs a 32-bit write to the specified, possibly unaligned I/O-type
+ address.
+
+ Writes the 32-bit I/O port specified by Port with the value specified by
+ Value and returns Value. This function must guarantee that all I/O read and
+ write operations are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port I/O port address
+ @param[in] Value 32-bit word to write
+
+ @return The value written to the I/O port.
+
+**/
+UINT32
+UnalignedIoWrite32 (
+ IN UINTN Port,
+ IN UINT32 Value
+ )
+{
+ __asm {
+ mov eax, dword ptr [Value]
+ mov dx, word ptr [Port]
+ out dx, eax
+ }
+
+ return Value;
+}
+
+/**
+ Reads a 32-bit word from the specified, possibly unaligned I/O-type address.
+
+ Reads the 32-bit I/O port specified by Port. The 32-bit read value is
+ returned. This function must guarantee that all I/O read and write operations
+ are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port The I/O port to read.
+
+ @return The value read.
+
+**/
+UINT32
+UnalignedIoRead32 (
+ IN UINTN Port
+ )
+{
+ UINT32 Data;
+
+ __asm {
+ mov dx, word ptr [Port]
+ in eax, dx
+ mov dword ptr [Data], eax
+ }
+
+ return Data;
+}
diff --git a/OvmfPkg/QemuVideoDxe/UnalignedIoInternal.h b/OvmfPkg/QemuVideoDxe/UnalignedIoInternal.h
new file mode 100644
index 0000000000..234de6c21b
--- /dev/null
+++ b/OvmfPkg/QemuVideoDxe/UnalignedIoInternal.h
@@ -0,0 +1,59 @@
+/** @file
+ Unaligned port I/O, with implementations for various x86 compilers and a
+ dummy for platforms which do not support unaligned port I/O.
+
+ Copyright (c) 2017, Phil Dennis-Jordan.
+ 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.
+
+**/
+
+#ifndef _UNALIGNED_IO_INTERNAL_H_
+#define _UNALIGNED_IO_INTERNAL_H_
+
+/**
+ Performs a 32-bit write to the specified, possibly unaligned I/O-type address.
+
+ Writes the 32-bit I/O port specified by Port with the value specified by Value
+ and returns Value. This function must guarantee that all I/O read and write
+ operations are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port I/O port address
+ @param[in] Value 32-bit word to write
+
+ @return The value written to the I/O port.
+
+**/
+UINT32
+UnalignedIoWrite32 (
+ IN UINTN Port,
+ IN UINT32 Value
+ );
+
+/**
+ Reads a 32-bit word from the specified, possibly unaligned I/O-type address.
+
+ Reads the 32-bit I/O port specified by Port. The 32-bit read value is
+ returned. This function must guarantee that all I/O read and write operations
+ are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port The I/O port to read.
+
+ @return The value read.
+
+**/
+UINT32
+UnalignedIoRead32 (
+ IN UINTN Port
+ );
+
+#endif
diff --git a/OvmfPkg/QemuVideoDxe/UnalignedIoMsc.c b/OvmfPkg/QemuVideoDxe/UnalignedIoMsc.c
new file mode 100644
index 0000000000..a466baee84
--- /dev/null
+++ b/OvmfPkg/QemuVideoDxe/UnalignedIoMsc.c
@@ -0,0 +1,78 @@
+/** @file
+ Unaligned port I/O. This file has compiler specifics for Microsoft C as there
+ is no ANSI C standard for doing IO.
+
+ Based on IoLibMsc.c
+
+ Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.
+ 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 "UnalignedIoInternal.h"
+
+unsigned long _inpd (unsigned short port);
+unsigned long _outpd (unsigned short port, unsigned long dataword );
+void _ReadWriteBarrier (void);
+
+/**
+ Performs a 32-bit write to the specified, possibly unaligned I/O-type
+ address.
+
+ Writes the 32-bit I/O port specified by Port with the value specified by
+ Value and returns Value. This function must guarantee that all I/O read and
+ write operations are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port I/O port address
+ @param[in] Value 32-bit word to write
+
+ @return The value written to the I/O port.
+
+**/
+UINT32
+UnalignedIoWrite32 (
+ IN UINTN Port,
+ IN UINT32 Value
+ )
+{
+ _ReadWriteBarrier ();
+ _outpd ((UINT16)Port, Value);
+ _ReadWriteBarrier ();
+ return Value;
+}
+
+/**
+ Reads a 32-bit word from the specified, possibly unaligned I/O-type address.
+
+ Reads the 32-bit I/O port specified by Port. The 32-bit read value is
+ returned. This function must guarantee that all I/O read and write operations
+ are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port The I/O port to read.
+
+ @return The value read.
+
+**/
+UINT32
+UnalignedIoRead32 (
+ IN UINTN Port
+ )
+{
+ UINT32 Value;
+
+ _ReadWriteBarrier ();
+ Value = _inpd ((UINT16)Port);
+ _ReadWriteBarrier ();
+ return Value;
+}
diff --git a/OvmfPkg/QemuVideoDxe/UnalignedIoUnsupported.c b/OvmfPkg/QemuVideoDxe/UnalignedIoUnsupported.c
new file mode 100644
index 0000000000..57560ab38f
--- /dev/null
+++ b/OvmfPkg/QemuVideoDxe/UnalignedIoUnsupported.c
@@ -0,0 +1,66 @@
+/** @file
+ Unaligned port I/O dummy implementation for platforms which do not support it.
+
+ Copyright (c) 2017, Phil Dennis-Jordan.
+ 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
+#include "UnalignedIoInternal.h"
+
+/**
+ Performs a 32-bit write to the specified, possibly unaligned I/O-type
+ address.
+
+ Writes the 32-bit I/O port specified by Port with the value specified by
+ Value and returns Value. This function must guarantee that all I/O read and
+ write operations are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port I/O port address
+ @param[in] Value 32-bit word to write
+
+ @return The value written to the I/O port.
+
+**/
+UINT32
+UnalignedIoWrite32 (
+ IN UINTN Port,
+ IN UINT32 Value
+ )
+{
+ ASSERT (FALSE);
+ return Value;
+}
+
+/**
+ Reads a 32-bit word from the specified, possibly unaligned I/O-type address.
+
+ Reads the 32-bit I/O port specified by Port. The 32-bit read value is
+ returned. This function must guarantee that all I/O read and write operations
+ are serialized.
+
+ If 32-bit unaligned I/O port operations are not supported, then ASSERT().
+
+ @param[in] Port The I/O port to read.
+
+ @return The value read.
+
+**/
+UINT32
+UnalignedIoRead32 (
+ IN UINTN Port
+ )
+{
+ ASSERT (FALSE);
+ return 0;
+}