OvmfPkg/IntelTdx: Update TDVF README

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4756

There are below updates in this patch:
1. Rename README to README.md so that it can be show as markdown
   document.
2. Update some information about TDVF.
2. Fix some typo.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

OvmfPkg/IntelTdx/README.md

@@ -1,13 +1,13 @@
 TDVF Overview
 -------------
 
-<b>Intel Trust Domain Extension (TDX)</b> is Intel Architecture extension
+**Intel Trust Domain Extension (TDX)** is Intel Architecture extension
 to provide trusted, isolated VM execution by removing CSP software
-(hypervisor etc) from the TCB. <b>TDX Virtual Firmware (TDVF)</b> is an
+(hypervisor etc) from the TCB. **TDX Virtual Firmware (TDVF)** is an
 EDK II based project to enable UEFI support for TDX based Virtual
 Machines. It provides the capability to launch a TD.
 
-The <b>Intel? TDX Virtual Firmware Design Guide</b> is at
+The **Intel TDX Virtual Firmware Design Guide** is at
 https://www.intel.com/content/dam/develop/external/us/en/documents/tdx-virtual-firmware-design-guide-rev-1.01.pdf.
 
 More information can be found at:
@@ -19,49 +19,61 @@ Configurations and Features
 
 There are 2 configurations for TDVF.
 
-<b>Config-A:</b>
+**Config-A:**
- - Merge the *basic* TDVF feature to existing OvmfX64Pkg.dsc. (Align
+ - Merge the *basic* TDVF feature to existing **OvmfPkgX64.dsc**. (Align
    with existing SEV)
- - Threat model: VMM is NOT out of TCB. (We don?t make things worse)
+ - Threat model: VMM is **NOT** out of TCB. (We don't make things worse)
- - The OvmfX64Pkg.dsc includes SEV/TDX/normal OVMF basic boot capability.
+ - The OvmfPkgX64.dsc includes SEV/TDX/normal OVMF basic boot capability.
    The final binary can run on SEV/TDX/normal OVMF.
  - No changes to existing OvmfPkgX64 image layout.
  - No need to remove features if they exist today.
- - PEI phase is NOT skipped in either Td or Non-Td.
+ - PEI phase is **NOT** skipped in either TD or Non-TD.
- - RTMR based measurement is supported.
+ - RTMR based measurement (CC_MEASUREMENT) is supported as an optional requirement.
  - External inputs from Host VMM are measured, such as TdHob, CFV.
  - Other external inputs are measured, such as FW_CFG data, os loader,
    initrd, etc.
 
-<b>Config-B:</b>
+**Config-B:**
- - Add a standalone IntelTdx.dsc to a TDX specific directory for a *full*
+ - Add a standalone **IntelTdxX64.dsc** to a TDX specific directory
-   feature TDVF.(Align with existing SEV)
+   (**OvmfPkg/IntelTdx**) for a *full* feature TDVF.(Align with existing SEV)
  - Threat model: VMM is out of TCB. (We need necessary change to prevent
    attack from VMM)
- - IntelTdx.dsc includes TDX/normal OVMF basic boot capability. The final
+ - IntelTdxX64.dsc includes TDX/normal OVMF basic boot capability. The final
    binary can run on TDX/normal OVMF.
  - It might eventually merge with AmdSev.dsc, but NOT at this point of
-   time. And we don?t know when it will happen. We need sync with AMD in
+   time. And we don't know when it will happen. We need sync with AMD in
    the community after both of us think the solutions are mature to merge.
- - Need to add necessary security feature as mandatory requirement, such
+ - RTMR based measurement (CC_MEASUREMENT) is supported as a mandatory requirement.
-   as RTMR based Trusted Boot support.
+ - External inputs from Host VMM are measured, such as TdHob, CFV.
- - Need to measure the external input from Host VMM, such as TdHob, CFV.
+ - Other external inputs are measured, such as FW_CFG data, os loader,
- - Need to measure other external input, such as FW_CFG data, os loader,
    initrd, etc.
- - Need to remove unnecessary attack surfaces, such as network stack.
+ - PEI phase is skipped to remove unnecessary attack surface.
+ - DXE FV is split into 2 FVs (DXEFV & NCCFV) to remove the unnecessary attack
+   surface in a TD guest..
+   - When launching a TD guest, only drivers in DXEFV are loaded.
+   - When launching a Non-TD guest, dirvers in both DXEFV and NCCFV are
+     loaded.
 
 Build
 ------
 - Build the TDVF (Config-A) target:
-`cd /path/to/edk2`
+```
-`source edksetup.sh`
+cd /path/to/edk2
-`build.sh -p OvmfPkg/OvmfPkgX64.dsc -a X64 -t GCC5`
+source edksetup.sh
+
+## without CC_MEASUREMENT enabled
+build -p OvmfPkg/OvmfPkgX64.dsc -a X64 -t GCC5 -b RELEASE
+
+## CC_MEASUREMENT enabled
+build -p OvmfPkg/OvmfPkgX64.dsc -a X64 -t GCC5 -D CC_MEASUREMENT_ENABLE=TRUE -b RELEASE
+```
 
 - Build the TDVF (Config-B) target:
-`cd /path/to/edk2`
+```
-`set PACKAGES_PATH=/path/to/edk2/OvmfPkg`
+cd /path/to/edk2
-`source edksetup.sh`
+source edksetup.sh
-`build.sh -p OvmfPkg/IntelTdx/IntelTdxX64.dsc -a X64 -t GCC5`
+build -p OvmfPkg/IntelTdx/IntelTdxX64.dsc -a X64 -t GCC5 -b RELEASE
+```
 
 Usage
 -----