OvmfPkg: Use TdHob instead of e820tables to get memory info in TDVF

[sunceping]

Currently, TDVF gets LowMemory and FistNonAddress from the e820tables
via fw_cfg, while TD-Hob can also provide the memory info of LowMemory
and FistNonAddress.

In current stage e820tables are not measured but TD-Hob is measured in
early phase by TDVF.

So, from the security perspective we'd better use the information from
TD-Hob instead of e820tables.

Cc: Erdem Aktas erdemaktas@google.com
Cc: Jiewen Yao jiewen.yao@intel.com
Cc: Min Xu min.m.xu@intel.com
Cc: Gerd Hoffmann kraxel@redhat.com
Cc: Elena Reshetova elena.reshetova@intel.com
Signed-off-by: Ceping Sun cepingx.sun@intel.com

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[kraxel]

Yes, the PlatformReservationConflict should not be needed when running on TDX:

For memory detection I'd suggest to use the cloud hypervisor idea, see PlatformScanE820Pvh. Have a relatively small helper function which reads the tdx hob, translates the entries to e820, goes call the callback with that. Should make the patch much smaller.

[sunceping]

For memory detection I'd suggest to use the cloud hypervisor idea, see PlatformScanE820Pvh. Have a relatively small helper function which reads the tdx hob, translates the entries to e820, goes call the callback with that. Should make the patch much smaller.

Thanks, now updated.

[kraxel]

Patch #1 looks good to me.
Patch #2 should not be needed any more due to patch #1 switching PlatformScanE820 to NOT use fw_cfg on TDX.

[sunceping]

Patch #1 looks good to me. Patch #2 should not be needed any more due to patch #1 switching PlatformScanE820 to NOT use fw_cfg on TDX.

Thanks, patch 2 has now been removed.