On Thu, Aug 19, 2021 at 02:27:16PM +0000, Min Xu wrote: > 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)
So basically the physical memory map. qemu has etc/e820 for that. > > 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. I can't see any support for Cloud-Hypervisor in OVMF. Also FreeBSD's bhyve doesn't support fw_cfg either and has its own ways to detect memory. Cloud-Hypervisor can surely do that too. So, why does this matter? > 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. Sure, but again, why does this matter? For qemu? I don't like the idea to have TDX take a completely different code paths. That increases the code complexity and makes testing harder for no good reason. take care, Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#79634): https://edk2.groups.io/g/devel/message/79634 Mute This Topic: https://groups.io/mt/84837914/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
