UefiCpuPkg: CpuIo2Dxe: optimize FIFO reads and writes of IO ports

UefiCpuPkg: CpuIo2Dxe: optimize FIFO reads and writes of IO ports

* Short description:

  The CpuIoServiceRead() and CpuIoServiceWrite() functions transfer data
  between memory and IO ports with individual Io(Read|Write)(8|16|32)
  function calls, each in an appropriately set up loop.

  On the Ia32 and X64 platforms however, FIFO reads and writes can be
  optimized, by coding them in assembly, and delegating the loop to the
  CPU, with the REP prefix.

  On KVM virtualization hosts, this difference has a huge performance
  impact: if the loop is open-coded, then the virtual machine traps to the
  hypervisor on every single UINT8 / UINT16 / UINT32 transfer, whereas
  with the REP prefix, KVM can transfer up to a page of data per VM trap.
  This is especially noticeable with IDE PIO transfers, where all the data
  are squeezed through IO ports.

* Long description:

  The RootBridgeIoIoRW() function in

    PcAtChipsetPkg/PciHostBridgeDxe/PciRootBridgeIo.c

  used to have the exact same IO port acces optimization, dating back
  verbatim to commit 1fd376d9792:

    PcAtChipsetPkg/PciHostBridgeDxe: Improve KVM FIFO I/O read/write
      performance

  OvmfPkg cloned the "PcAtChipsetPkg/PciHostBridgeDxe" driver (for
  unrelated reasons), and inherited the optimization from PcAtChipsetPkg.

  The "PcAtChipsetPkg/PciHostBridgeDxe" driver was ultimately removed in
  commit 111d79db47:

    PcAtChipsetPkg/PciHostBridge: Remove PciHostBridge driver

  and OvmfPkg too was rebased to the new core Pci Host Bridge Driver, in
  commit 4014885ffd:

    OvmfPkg: switch to MdeModulePkg/Bus/Pci/PciHostBridgeDxe

  This caused the optimization to go lost. Namely, the
  RootBridgeIoIoRead() and RootBridgeIoIoWrite() functions in the new core
  Pci Host Bridge Driver delegate IO port accesses to
  EFI_CPU_IO2_PROTOCOL. And, in OvmfPkg (and likely most other Ia32 / X64
  edk2 platforms), this protocol is provided by "UefiCpuPkg/CpuIo2Dxe",
  which lacks the optimization.

  Therefore, this patch ports the C source code logic from commit
  1fd376d9792 (see above) to "UefiCpuPkg/CpuIo2Dxe", plus it ports the
  NASM-converted assembly helper functions from OvmfPkg commits
  6026bf460037 and ace1d0517b65:

    OvmfPkg PciHostBridgeDxe: Convert Ia32/IoFifo.asm to NASM

    OvmfPkg PciHostBridgeDxe: Convert X64/IoFifo.asm to NASM

  In order to support the MSFT and INTEL toolchains as well, the *.asm
  files are ported from OvmfPkg as well, immediately from before the above
  conversion (that is, at 6026bf460037^).

* Notes about the port:

  - The write and read branches from commit 1fd376d9792 are split to the
    separate functions CpuIoServiceWrite() and CpuIoServiceRead().

  - The EfiPciWidthUintXX constants are replaced with EfiCpuIoWidthUintXX.

  - The cast expression "(UINTN) Address" is replaced with
    "(UINTN)Address" (i.e., no space), because that's how the receiving
    functions spell it as well.

  - The labels in the switch statements are unindented by one level, to
    match the edk2 coding style (and the rest of UefiCpuPkg) better.

* The first signoff belongs to Jordan, because he authored all of
  1fd376d9792, 6026bf460037 and ace1d0517b65.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Ref: https://www.redhat.com/archives/vfio-users/2016-April/msg00029.html
Reported-by: Mark <kram321@gmail.com>
Ref: http://thread.gmane.org/gmane.comp.bios.edk2.devel/10424/focus=10432
Reported-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Mark <kram321@gmail.com>
Tested-by: Mark <kram321@gmail.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>