Re: [PATCH] MdePkg/BaseIoLibIntrinsic: make BaseIoLibIntrinsic safe for ArmVirt/KVM

["Gao, Liming" <liming.gao@intel.com>]

Laszlo:
  I get your point. I am OK to add this library instance in MdePkg for code sharing. 

Ard:
  Have you plan to make this library instance pass VS2017 tool chain? 

Thanks
Liming
> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Friday, June 8, 2018 12:56 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Gao, Liming <liming.gao@intel.com>
> Cc: edk2-devel@lists.01.org; leif.lindholm@linaro.org; Kinney, Michael D <michael.d.kinney@intel.com>
> Subject: Re: [PATCH] MdePkg/BaseIoLibIntrinsic: make BaseIoLibIntrinsic safe for ArmVirt/KVM
> 
> On 06/07/18 17:09, Ard Biesheuvel wrote:
> > On 7 June 2018 at 17:08, Gao, Liming <liming.gao@intel.com> wrote:
> >> Ard:
> >>   If this library instance is specific to ARM emulator with KVM, how about add it into ArmVirtPkg?
> >>
> >
> > Laszlo, do you want to take this question?
> 
> Certainly.
> 
> Liming, in commit b6d11d7c4678, we added "BaseIoLibIntrinsicSev.inf" to
> "MdePkg/Library/BaseIoLibIntrinsic", with some custom Ia32 and X64 NASM
> files, but mostly reusing the large existent files ("IoLibMmioBuffer.c",
> "IoHighLevel.c" etc).
> 
> That library instance (and the NASM customizations) target AMD SEV; that
> is, when the code runs in a virtual machine for which AMD Secure
> Encrypted Virtualization is enabled. The NASM code uses CPUID to
> dynamically determine whether it runs in a SEV guest, or in a normal
> guest, and in the former case, it avoids using the REP prefix in the
> IoFifo routines (it uses open-coded LOOPs).
> 
> The "BaseIoLibIntrinsicSev.inf" instance is only ever used in OvmfPkg
> (it only makes sense in virtual machines), but the consensus back then
> was to add the lib instance to MdePkg.
> 
> 
> This time, Ard has already implemented (and posted) the IoLib instance
> that we need for ARM KVM such that it lands under ArmVirtPkg -- however,
> that library instance duplicates a huge amount of code, un-changed, from
> "BaseIoLibIntrinsic" (such as "IoLibMmioBuffer.c", "IoHighLevel.c"). I
> suggested that Ard instead post the new library instance as a new INF
> file (plus some assembly files) for BaseIoLibIntrinsic itself, because:
> (a) this way we avoid code duplication, and (b) that's exactly what we
> did -- for another virtualization-only use case -- in commit
> b6d11d7c4678 earlier.
> 
> If you'd like us to add the code to ArmVirtPkg, I don't think that's the
> right or consequent action, but technically, we can simply fall back to
> the ArmVirtPkg patches that Ard already wrote and posted.
> 
> Thanks,
> Laszlo
> 
> >>> -----Original Message-----
> >>> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> >>> Sent: Thursday, June 7, 2018 6:47 PM
> >>> To: edk2-devel@lists.01.org
> >>> Cc: lersek@redhat.com; leif.lindholm@linaro.org; Gao, Liming <liming.gao@intel.com>; Kinney, Michael D
> >>> <michael.d.kinney@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>> Subject: [PATCH] MdePkg/BaseIoLibIntrinsic: make BaseIoLibIntrinsic safe for ArmVirt/KVM
> >>>
> >>> KVM on ARM refuses to decode load/store instructions used to perform
> >>> I/O to emulated devices, and instead relies on the exception syndrome
> >>> information to describe the operand register, access size, etc.
> >>> This is only possible for instructions that have a single input/output
> >>> register (as opposed to ones that increment the offset register, or
> >>> load/store pair instructions, etc). Otherwise, QEMU crashes with the
> >>> following error
> >>>
> >>>   error: kvm run failed Function not implemented
> >>>   R00=01010101 R01=00000008 R02=00000048 R03=08000820
> >>>   R04=00000120 R05=7faaa0e0 R06=7faaa0dc R07=7faaa0e8
> >>>   R08=7faaa0ec R09=7faaa088 R10=000000ff R11=00000080
> >>>   R12=ff000000 R13=7fccfe08 R14=7faa835f R15=7faa887c
> >>>   PSR=800001f3 N--- T svc32
> >>>   QEMU: Terminated
> >>>
> >>> and KVM produces a warning such as the following in the kernel log
> >>>
> >>>   kvm [17646]: load/store instruction decoding not implemented
> >>>
> >>> The IoLib implementation provided by MdePkg/Library/BaseIoLibIntrinsic
> >>> is based on C code, and when LTO is in effect, the MMIO accesses could
> >>> be merged with, e.g., manipulations of the loop counter, producing
> >>> opcodes that KVM does not support for emulated MMIO.
> >>>
> >>> So let's add a special ArmVirt flavor of this library that implements
> >>> that actual load/store operations in assembler, ensuring that the
> >>> instructions involved can be emulated by KVM.
> >>>
> >>> Contributed-under: TianoCore Contribution Agreement 1.1
> >>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>> ---
> >>>  ArmVirtPkg/ArmVirt.dsc.inc                                      |   2 +-
> >>>  MdePkg/Library/BaseIoLibIntrinsic/AArch64/ArmVirtMmio.S         | 164 +++++
> >>>  MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.S             | 161 +++++
> >>>  MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.asm           | 165 +++++
> >>>  MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicArmVirt.inf |  50 ++
> >>>  MdePkg/Library/BaseIoLibIntrinsic/IoLibArmVirt.c                | 641 ++++++++++++++++++++
> >>>  6 files changed, 1182 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/ArmVirtPkg/ArmVirt.dsc.inc b/ArmVirtPkg/ArmVirt.dsc.inc
> >>> index 766e4f598a07..7464ac70ed1b 100644
> >>> --- a/ArmVirtPkg/ArmVirt.dsc.inc
> >>> +++ b/ArmVirtPkg/ArmVirt.dsc.inc
> >>> @@ -41,7 +41,7 @@ [LibraryClasses.common]
> >>>    PrintLib|MdePkg/Library/BasePrintLib/BasePrintLib.inf
> >>>    PeCoffGetEntryPointLib|MdePkg/Library/BasePeCoffGetEntryPointLib/BasePeCoffGetEntryPointLib.inf
> >>>    PeCoffLib|MdePkg/Library/BasePeCoffLib/BasePeCoffLib.inf
> >>> -  IoLib|MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsic.inf
> >>> +  IoLib|MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicArmVirt.inf
> >>>    UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
> >>>    CpuLib|MdePkg/Library/BaseCpuLib/BaseCpuLib.inf
> >>>
> >>> diff --git a/MdePkg/Library/BaseIoLibIntrinsic/AArch64/ArmVirtMmio.S
> b/MdePkg/Library/BaseIoLibIntrinsic/AArch64/ArmVirtMmio.S
> >>> new file mode 100644
> >>> index 000000000000..47be68a3e783
> >>> --- /dev/null
> >>> +++ b/MdePkg/Library/BaseIoLibIntrinsic/AArch64/ArmVirtMmio.S
> >>> @@ -0,0 +1,164 @@
> >>> +#
> >>> +#  Copyright (c) 2014-2018, Linaro Limited. 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.
> >>> +#
> >>> +#
> >>> +
> >>> +.text
> >>> +.align 3
> >>> +
> >>> +GCC_ASM_EXPORT(MmioRead8Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite8Internal)
> >>> +GCC_ASM_EXPORT(MmioRead16Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite16Internal)
> >>> +GCC_ASM_EXPORT(MmioRead32Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite32Internal)
> >>> +GCC_ASM_EXPORT(MmioRead64Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite64Internal)
> >>> +
> >>> +//
> >>> +//  Reads an 8-bit MMIO register.
> >>> +//
> >>> +//  Reads the 8-bit MMIO register specified by Address. The 8-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead8Internal):
> >>> +  ldrb    w0, [x0]
> >>> +  dmb     ld
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Writes an 8-bit MMIO register.
> >>> +//
> >>> +//  Writes the 8-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite8Internal):
> >>> +  dmb     st
> >>> +  strb    w1, [x0]
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Reads a 16-bit MMIO register.
> >>> +//
> >>> +//  Reads the 16-bit MMIO register specified by Address. The 16-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead16Internal):
> >>> +  ldrh    w0, [x0]
> >>> +  dmb     ld
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Writes a 16-bit MMIO register.
> >>> +//
> >>> +//  Writes the 16-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite16Internal):
> >>> +  dmb     st
> >>> +  strh    w1, [x0]
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Reads a 32-bit MMIO register.
> >>> +//
> >>> +//  Reads the 32-bit MMIO register specified by Address. The 32-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead32Internal):
> >>> +  ldr     w0, [x0]
> >>> +  dmb     ld
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Writes a 32-bit MMIO register.
> >>> +//
> >>> +//  Writes the 32-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite32Internal):
> >>> +  dmb     st
> >>> +  str     w1, [x0]
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Reads a 64-bit MMIO register.
> >>> +//
> >>> +//  Reads the 64-bit MMIO register specified by Address. The 64-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead64Internal):
> >>> +  ldr     x0, [x0]
> >>> +  dmb     ld
> >>> +  ret
> >>> +
> >>> +//
> >>> +//  Writes a 64-bit MMIO register.
> >>> +//
> >>> +//  Writes the 64-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite64Internal):
> >>> +  dmb     st
> >>> +  str     x1, [x0]
> >>> +  ret
> >>> diff --git a/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.S b/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.S
> >>> new file mode 100644
> >>> index 000000000000..438805ca7c24
> >>> --- /dev/null
> >>> +++ b/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.S
> >>> @@ -0,0 +1,161 @@
> >>> +#
> >>> +#  Copyright (c) 2014-2018, Linaro Limited. 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.
> >>> +#
> >>> +#
> >>> +
> >>> +GCC_ASM_EXPORT(MmioRead8Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite8Internal)
> >>> +GCC_ASM_EXPORT(MmioRead16Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite16Internal)
> >>> +GCC_ASM_EXPORT(MmioRead32Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite32Internal)
> >>> +GCC_ASM_EXPORT(MmioRead64Internal)
> >>> +GCC_ASM_EXPORT(MmioWrite64Internal)
> >>> +
> >>> +//
> >>> +//  Reads an 8-bit MMIO register.
> >>> +//
> >>> +//  Reads the 8-bit MMIO register specified by Address. The 8-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead8Internal):
> >>> +  ldrb    r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Writes an 8-bit MMIO register.
> >>> +//
> >>> +//  Writes the 8-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite8Internal):
> >>> +  dmb     st
> >>> +  strb    r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Reads a 16-bit MMIO register.
> >>> +//
> >>> +//  Reads the 16-bit MMIO register specified by Address. The 16-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead16Internal):
> >>> +  ldrh    r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Writes a 16-bit MMIO register.
> >>> +//
> >>> +//  Writes the 16-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite16Internal):
> >>> +  dmb     st
> >>> +  strh    r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Reads a 32-bit MMIO register.
> >>> +//
> >>> +//  Reads the 32-bit MMIO register specified by Address. The 32-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead32Internal):
> >>> +  ldr     r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Writes a 32-bit MMIO register.
> >>> +//
> >>> +//  Writes the 32-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite32Internal):
> >>> +  dmb     st
> >>> +  str     r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Reads a 64-bit MMIO register.
> >>> +//
> >>> +//  Reads the 64-bit MMIO register specified by Address. The 64-bit read value is
> >>> +//  returned. This function must guarantee that all MMIO read and write
> >>> +//  operations are serialized.
> >>> +//
> >>> +//  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to read.
> >>> +//
> >>> +//  @return The value read.
> >>> +//
> >>> +ASM_PFX(MmioRead64Internal):
> >>> +  ldrd    r0, r1, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +//
> >>> +//  Writes a 64-bit MMIO register.
> >>> +//
> >>> +//  Writes the 64-bit MMIO register specified by Address with the value specified
> >>> +//  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +//  and write operations are serialized.
> >>> +//
> >>> +//  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +//
> >>> +//  @param  Address The MMIO register to write.
> >>> +//  @param  Value   The value to write to the MMIO register.
> >>> +//
> >>> +ASM_PFX(MmioWrite64Internal):
> >>> +  dmb     st
> >>> +  strd    r2, r3, [r0]
> >>> +  bx      lr
> >>> diff --git a/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.asm
> b/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.asm
> >>> new file mode 100644
> >>> index 000000000000..82add82f800a
> >>> --- /dev/null
> >>> +++ b/MdePkg/Library/BaseIoLibIntrinsic/Arm/ArmVirtMmio.asm
> >>> @@ -0,0 +1,165 @@
> >>> +;
> >>> +;  Copyright (c) 2014-2018, Linaro Limited. 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.
> >>> +;
> >>> +
> >>> +
> >>> +AREA IoLibMmio, CODE, READONLY
> >>> +
> >>> +EXPORT MmioRead8Internal
> >>> +EXPORT MmioWrite8Internal
> >>> +EXPORT MmioRead16Internal
> >>> +EXPORT MmioWrite16Internal
> >>> +EXPORT MmioRead32Internal
> >>> +EXPORT MmioWrite32Internal
> >>> +EXPORT MmioRead64Internal
> >>> +EXPORT MmioWrite64Internal
> >>> +
> >>> +;
> >>> +;  Reads an 8-bit MMIO register.
> >>> +;
> >>> +;  Reads the 8-bit MMIO register specified by Address. The 8-bit read value is
> >>> +;  returned. This function must guarantee that all MMIO read and write
> >>> +;  operations are serialized.
> >>> +;
> >>> +;  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to read.
> >>> +;
> >>> +;  @return The value read.
> >>> +;
> >>> +MmioRead8Internal
> >>> +  ldrb    r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Writes an 8-bit MMIO register.
> >>> +;
> >>> +;  Writes the 8-bit MMIO register specified by Address with the value specified
> >>> +;  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +;  and write operations are serialized.
> >>> +;
> >>> +;  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to write.
> >>> +;  @param  Value   The value to write to the MMIO register.
> >>> +;
> >>> +MmioWrite8Internal
> >>> +  dmb     st
> >>> +  strb    r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Reads a 16-bit MMIO register.
> >>> +;
> >>> +;  Reads the 16-bit MMIO register specified by Address. The 16-bit read value is
> >>> +;  returned. This function must guarantee that all MMIO read and write
> >>> +;  operations are serialized.
> >>> +;
> >>> +;  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to read.
> >>> +;
> >>> +;  @return The value read.
> >>> +;
> >>> +MmioRead16Internal
> >>> +  ldrh    r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Writes a 16-bit MMIO register.
> >>> +;
> >>> +;  Writes the 16-bit MMIO register specified by Address with the value specified
> >>> +;  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +;  and write operations are serialized.
> >>> +;
> >>> +;  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to write.
> >>> +;  @param  Value   The value to write to the MMIO register.
> >>> +;
> >>> +MmioWrite16Internal
> >>> +  dmb     st
> >>> +  strh    r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Reads a 32-bit MMIO register.
> >>> +;
> >>> +;  Reads the 32-bit MMIO register specified by Address. The 32-bit read value is
> >>> +;  returned. This function must guarantee that all MMIO read and write
> >>> +;  operations are serialized.
> >>> +;
> >>> +;  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to read.
> >>> +;
> >>> +;  @return The value read.
> >>> +;
> >>> +MmioRead32Internal
> >>> +  ldr     r0, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Writes a 32-bit MMIO register.
> >>> +;
> >>> +;  Writes the 32-bit MMIO register specified by Address with the value specified
> >>> +;  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +;  and write operations are serialized.
> >>> +;
> >>> +;  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to write.
> >>> +;  @param  Value   The value to write to the MMIO register.
> >>> +;
> >>> +MmioWrite32Internal
> >>> +  dmb     st
> >>> +  str     r1, [r0]
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Reads a 64-bit MMIO register.
> >>> +;
> >>> +;  Reads the 64-bit MMIO register specified by Address. The 64-bit read value is
> >>> +;  returned. This function must guarantee that all MMIO read and write
> >>> +;  operations are serialized.
> >>> +;
> >>> +;  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to read.
> >>> +;
> >>> +;  @return The value read.
> >>> +;
> >>> +MmioRead64Internal
> >>> +  ldrd    r0, r1, [r0]
> >>> +  dmb
> >>> +  bx      lr
> >>> +
> >>> +;
> >>> +;  Writes a 64-bit MMIO register.
> >>> +;
> >>> +;  Writes the 64-bit MMIO register specified by Address with the value specified
> >>> +;  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +;  and write operations are serialized.
> >>> +;
> >>> +;  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +;
> >>> +;  @param  Address The MMIO register to write.
> >>> +;  @param  Value   The value to write to the MMIO register.
> >>> +;
> >>> +MmioWrite64Internal
> >>> +  dmb     st
> >>> +  strd    r2, r3, [r0]
> >>> +  bx      lr
> >>> +
> >>> +  END
> >>> diff --git a/MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicArmVirt.inf
> >>> b/MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicArmVirt.inf
> >>> new file mode 100644
> >>> index 000000000000..5a1dc87ed2bd
> >>> --- /dev/null
> >>> +++ b/MdePkg/Library/BaseIoLibIntrinsic/BaseIoLibIntrinsicArmVirt.inf
> >>> @@ -0,0 +1,50 @@
> >>> +## @file
> >>> +#  Instance of I/O Library using KVM/ARM safe assembler routines
> >>> +#
> >>> +#  Copyright (c) 2007 - 2015, Intel Corporation. All rights reserved.<BR>
> >>> +#  Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
> >>> +#  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
> >>> +#  Copyright (c) 2018, 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                    = 0x0001001A
> >>> +  BASE_NAME                      = BaseIoLibIntrinsicArmVirt
> >>> +  FILE_GUID                      = 217102b4-b465-4a1d-a2de-93dd385ec480
> >>> +  MODULE_TYPE                    = BASE
> >>> +  VERSION_STRING                 = 1.0
> >>> +  LIBRARY_CLASS                  = IoLib
> >>> +
> >>> +#
> >>> +#  VALID_ARCHITECTURES           = ARM AARCH64
> >>> +#
> >>> +
> >>> +[Sources]
> >>> +  IoLibMmioBuffer.c
> >>> +  BaseIoLibIntrinsicInternal.h
> >>> +  IoHighLevel.c
> >>> +
> >>> +[Sources.ARM]
> >>> +  IoLibArmVirt.c
> >>> +  Arm/ArmVirtMmio.S   | GCC
> >>> +  Arm/ArmVirtMmio.asm | RVCT
> >>> +
> >>> +[Sources.AARCH64]
> >>> +  IoLibArmVirt.c
> >>> +  AArch64/ArmVirtMmio.S
> >>> +
> >>> +[Packages]
> >>> +  MdePkg/MdePkg.dec
> >>> +
> >>> +[LibraryClasses]
> >>> +  DebugLib
> >>> +  BaseLib
> >>> diff --git a/MdePkg/Library/BaseIoLibIntrinsic/IoLibArmVirt.c b/MdePkg/Library/BaseIoLibIntrinsic/IoLibArmVirt.c
> >>> new file mode 100644
> >>> index 000000000000..154d583246ac
> >>> --- /dev/null
> >>> +++ b/MdePkg/Library/BaseIoLibIntrinsic/IoLibArmVirt.c
> >>> @@ -0,0 +1,641 @@
> >>> +/** @file
> >>> +  I/O Library for ARM.
> >>> +
> >>> +  Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
> >>> +  Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
> >>> +  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
> >>> +  Copyright (c) 2018, 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 "BaseIoLibIntrinsicInternal.h"
> >>> +
> >>> +UINT8
> >>> +EFIAPI
> >>> +MmioRead8Internal (
> >>> +  IN      UINTN                     Address
> >>> +  );
> >>> +
> >>> +VOID
> >>> +EFIAPI
> >>> +MmioWrite8Internal (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT8                     Value
> >>> +  );
> >>> +
> >>> +UINT16
> >>> +EFIAPI
> >>> +MmioRead16Internal (
> >>> +  IN      UINTN                     Address
> >>> +  );
> >>> +
> >>> +VOID
> >>> +EFIAPI
> >>> +MmioWrite16Internal (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT16                    Value
> >>> +  );
> >>> +
> >>> +UINT32
> >>> +EFIAPI
> >>> +MmioRead32Internal (
> >>> +  IN      UINTN                     Address
> >>> +  );
> >>> +
> >>> +VOID
> >>> +EFIAPI
> >>> +MmioWrite32Internal (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT32                    Value
> >>> +  );
> >>> +
> >>> +UINT64
> >>> +EFIAPI
> >>> +MmioRead64Internal (
> >>> +  IN      UINTN                     Address
> >>> +  );
> >>> +
> >>> +VOID
> >>> +EFIAPI
> >>> +MmioWrite64Internal (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT64                    Value
> >>> +  );
> >>> +
> >>> +/**
> >>> +  Reads an 8-bit I/O port.
> >>> +
> >>> +  Reads the 8-bit I/O port specified by Port. The 8-bit read value is returned.
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 8-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT8
> >>> +EFIAPI
> >>> +IoRead8 (
> >>> +  IN      UINTN                     Port
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes an 8-bit I/O port.
> >>> +
> >>> +  Writes the 8-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 8-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to write.
> >>> +  @param  Value The value to write to the I/O port.
> >>> +
> >>> +  @return The value written the I/O port.
> >>> +
> >>> +**/
> >>> +UINT8
> >>> +EFIAPI
> >>> +IoWrite8 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINT8                     Value
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 16-bit I/O port.
> >>> +
> >>> +  Reads the 16-bit I/O port specified by Port. The 16-bit read value is returned.
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 16-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT16
> >>> +EFIAPI
> >>> +IoRead16 (
> >>> +  IN      UINTN                     Port
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 16-bit I/O port.
> >>> +
> >>> +  Writes the 16-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 16-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to write.
> >>> +  @param  Value The value to write to the I/O port.
> >>> +
> >>> +  @return The value written the I/O port.
> >>> +
> >>> +**/
> >>> +UINT16
> >>> +EFIAPI
> >>> +IoWrite16 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINT16                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 32-bit I/O port.
> >>> +
> >>> +  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 I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT32
> >>> +EFIAPI
> >>> +IoRead32 (
> >>> +  IN      UINTN                     Port
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 32-bit I/O port.
> >>> +
> >>> +  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 I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to write.
> >>> +  @param  Value The value to write to the I/O port.
> >>> +
> >>> +  @return The value written the I/O port.
> >>> +
> >>> +**/
> >>> +UINT32
> >>> +EFIAPI
> >>> +IoWrite32 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINT32                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 64-bit I/O port.
> >>> +
> >>> +  Reads the 64-bit I/O port specified by Port. The 64-bit read value is returned.
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 64-bit I/O port operations are not supported, then ASSERT().
> >>> +  If Port is not aligned on a 64-bit boundary, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT64
> >>> +EFIAPI
> >>> +IoRead64 (
> >>> +  IN      UINTN                     Port
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 64-bit I/O port.
> >>> +
> >>> +  Writes the 64-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 64-bit I/O port operations are not supported, then ASSERT().
> >>> +  If Port is not aligned on a 64-bit boundary, then ASSERT().
> >>> +
> >>> +  @param  Port  The I/O port to write.
> >>> +  @param  Value The value to write to the I/O port.
> >>> +
> >>> +  @return The value written to the I/O port.
> >>> +
> >>> +**/
> >>> +UINT64
> >>> +EFIAPI
> >>> +IoWrite64 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINT64                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +  return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads an 8-bit I/O port fifo into a block of memory.
> >>> +
> >>> +  Reads the 8-bit I/O fifo port specified by Port.
> >>> +  The port is read Count times, and the read data is
> >>> +  stored in the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 8-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to read.
> >>> +  @param  Count   The number of times to read I/O port.
> >>> +  @param  Buffer  The buffer to store the read data into.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoReadFifo8 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  OUT     VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a block of memory into an 8-bit I/O port fifo.
> >>> +
> >>> +  Writes the 8-bit I/O fifo port specified by Port.
> >>> +  The port is written Count times, and the write data is
> >>> +  retrieved from the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O write and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 8-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to write.
> >>> +  @param  Count   The number of times to write I/O port.
> >>> +  @param  Buffer  The buffer to retrieve the write data from.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoWriteFifo8 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  IN      VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 16-bit I/O port fifo into a block of memory.
> >>> +
> >>> +  Reads the 16-bit I/O fifo port specified by Port.
> >>> +  The port is read Count times, and the read data is
> >>> +  stored in the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 16-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to read.
> >>> +  @param  Count   The number of times to read I/O port.
> >>> +  @param  Buffer  The buffer to store the read data into.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoReadFifo16 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  OUT     VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a block of memory into a 16-bit I/O port fifo.
> >>> +
> >>> +  Writes the 16-bit I/O fifo port specified by Port.
> >>> +  The port is written Count times, and the write data is
> >>> +  retrieved from the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O write and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 16-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to write.
> >>> +  @param  Count   The number of times to write I/O port.
> >>> +  @param  Buffer  The buffer to retrieve the write data from.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoWriteFifo16 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  IN      VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 32-bit I/O port fifo into a block of memory.
> >>> +
> >>> +  Reads the 32-bit I/O fifo port specified by Port.
> >>> +  The port is read Count times, and the read data is
> >>> +  stored in the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O read and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 32-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to read.
> >>> +  @param  Count   The number of times to read I/O port.
> >>> +  @param  Buffer  The buffer to store the read data into.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoReadFifo32 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  OUT     VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a block of memory into a 32-bit I/O port fifo.
> >>> +
> >>> +  Writes the 32-bit I/O fifo port specified by Port.
> >>> +  The port is written Count times, and the write data is
> >>> +  retrieved from the provided Buffer.
> >>> +
> >>> +  This function must guarantee that all I/O write and write operations are
> >>> +  serialized.
> >>> +
> >>> +  If 32-bit I/O port operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Port    The I/O port to write.
> >>> +  @param  Count   The number of times to write I/O port.
> >>> +  @param  Buffer  The buffer to retrieve the write data from.
> >>> +
> >>> +**/
> >>> +VOID
> >>> +EFIAPI
> >>> +IoWriteFifo32 (
> >>> +  IN      UINTN                     Port,
> >>> +  IN      UINTN                     Count,
> >>> +  IN      VOID                      *Buffer
> >>> +  )
> >>> +{
> >>> +  ASSERT (FALSE);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads an 8-bit MMIO register.
> >>> +
> >>> +  Reads the 8-bit MMIO register specified by Address. The 8-bit read value is
> >>> +  returned. This function must guarantee that all MMIO read and write
> >>> +  operations are serialized.
> >>> +
> >>> +  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT8
> >>> +EFIAPI
> >>> +MmioRead8 (
> >>> +  IN      UINTN                     Address
> >>> +  )
> >>> +{
> >>> +  return MmioRead8Internal (Address);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes an 8-bit MMIO register.
> >>> +
> >>> +  Writes the 8-bit MMIO register specified by Address with the value specified
> >>> +  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +  and write operations are serialized.
> >>> +
> >>> +  If 8-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to write.
> >>> +  @param  Value   The value to write to the MMIO register.
> >>> +
> >>> +**/
> >>> +UINT8
> >>> +EFIAPI
> >>> +MmioWrite8 (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT8                     Value
> >>> +  )
> >>> +{
> >>> +  MmioWrite8Internal (Address, Value);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 16-bit MMIO register.
> >>> +
> >>> +  Reads the 16-bit MMIO register specified by Address. The 16-bit read value is
> >>> +  returned. This function must guarantee that all MMIO read and write
> >>> +  operations are serialized.
> >>> +
> >>> +  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT16
> >>> +EFIAPI
> >>> +MmioRead16 (
> >>> +  IN      UINTN                     Address
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 1) == 0);
> >>> +
> >>> +  return MmioRead16Internal (Address);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 16-bit MMIO register.
> >>> +
> >>> +  Writes the 16-bit MMIO register specified by Address with the value specified
> >>> +  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +  and write operations are serialized.
> >>> +
> >>> +  If 16-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to write.
> >>> +  @param  Value   The value to write to the MMIO register.
> >>> +
> >>> +**/
> >>> +UINT16
> >>> +EFIAPI
> >>> +MmioWrite16 (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT16                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 1) == 0);
> >>> +
> >>> +  MmioWrite16Internal (Address, Value);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 32-bit MMIO register.
> >>> +
> >>> +  Reads the 32-bit MMIO register specified by Address. The 32-bit read value is
> >>> +  returned. This function must guarantee that all MMIO read and write
> >>> +  operations are serialized.
> >>> +
> >>> +  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT32
> >>> +EFIAPI
> >>> +MmioRead32 (
> >>> +  IN      UINTN                     Address
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 3) == 0);
> >>> +
> >>> +  return MmioRead32Internal (Address);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 32-bit MMIO register.
> >>> +
> >>> +  Writes the 32-bit MMIO register specified by Address with the value specified
> >>> +  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +  and write operations are serialized.
> >>> +
> >>> +  If 32-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to write.
> >>> +  @param  Value   The value to write to the MMIO register.
> >>> +
> >>> +**/
> >>> +UINT32
> >>> +EFIAPI
> >>> +MmioWrite32 (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT32                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 3) == 0);
> >>> +
> >>> +  MmioWrite32Internal (Address, Value);
> >>> +  return Value;
> >>> +}
> >>> +
> >>> +/**
> >>> +  Reads a 64-bit MMIO register.
> >>> +
> >>> +  Reads the 64-bit MMIO register specified by Address. The 64-bit read value is
> >>> +  returned. This function must guarantee that all MMIO read and write
> >>> +  operations are serialized.
> >>> +
> >>> +  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to read.
> >>> +
> >>> +  @return The value read.
> >>> +
> >>> +**/
> >>> +UINT64
> >>> +EFIAPI
> >>> +MmioRead64 (
> >>> +  IN      UINTN                     Address
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 7) == 0);
> >>> +
> >>> +  return MmioRead64Internal (Address);
> >>> +}
> >>> +
> >>> +/**
> >>> +  Writes a 64-bit MMIO register.
> >>> +
> >>> +  Writes the 64-bit MMIO register specified by Address with the value specified
> >>> +  by Value and returns Value. This function must guarantee that all MMIO read
> >>> +  and write operations are serialized.
> >>> +
> >>> +  If 64-bit MMIO register operations are not supported, then ASSERT().
> >>> +
> >>> +  @param  Address The MMIO register to write.
> >>> +  @param  Value   The value to write to the MMIO register.
> >>> +
> >>> +**/
> >>> +UINT64
> >>> +EFIAPI
> >>> +MmioWrite64 (
> >>> +  IN      UINTN                     Address,
> >>> +  IN      UINT64                    Value
> >>> +  )
> >>> +{
> >>> +  ASSERT ((Address & 7) == 0);
> >>> +
> >>> +  MmioWrite64Internal (Address, Value);
> >>> +  return Value;
> >>> +}
> >>> --
> >>> 2.17.0
> >>