On August 19, 2021 2:50 PM, Gerd Hoffmann wrote: > > +/** > > + In Tdx guest, some information need to be passed from host VMM to > guest > > + firmware. For example, the memory resource, etc. These information are > > + prepared by host VMM and put in HobList which is described in > TdxMetadata. > > What kind of information is passed to the guest here? Please see https://software.intel.com/content/dam/develop/external/us/en/documents/tdx-virtual-firmware-design-guide-rev-1.pdf Section 4.2 TD Hand-Off Block (HOB) > > qemu has fw_cfg to pass information from the VMM to the guest firmware. > What are the reasons to not use fw_cfg? Not all the VMM support fw_cfg. Cloud-Hypervisor is the example. https://github.com/cloud-hypervisor/cloud-hypervisor TD Hob list gives Cloud-Hypervisor a chance to pass information to guest firmware. For example, ACPI can be downloaded from QEMU via fw_cfg to firmware. But Cloud-Hypervisor cannot pass ACPI via fw_cfg. In this situation, TD Hob can resolve this problem. > > thanks, > Gerd
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