On 04/07/21 15:22, Laszlo Ersek wrote: > On 04/07/21 02:21, Xu, Min M wrote: > >> Intel TDX also has metadata which is consumed by QEMU. We put the metadata >> in a single file (TdxMetadata.asm) and put it at the end of ResetVectorVtf0. >> Then a pointer is placed in a known location in ResetVector.nasm. In this way >> QEMU can easily read the Metadata by the pointer. >> ------------------------------------------------------------------ >> ALIGN 8 >> ; >> ; TDX Virtual Firmware injects metadata in VTF0. >> ; The address of the metadata is injected in this location (0xffffffe8) >> ; >> DD (OVMF_IMAGE_SIZE_IN_KB * 1024 - (fourGigabytes - TdxMetadataGuid >> - 16)) >> ; >> ; The VTF signature >> ; >> ; VTF-0 means that the VTF (Volume Top File) code does not require >> ; any fixups. >> ; >> vtfSignature: >> DB 'V', 'T', 'F', 0 >> ------------------------------------------------------------------ >> >> The space in ResetVector is very precious and we all want a known location >> so that QEMU >> can find the metadata easily. Putting the metadata in a single file give the >> developers >> more flexible (They can put anything they want). So I think a pointer (point >> to a metadata >> file) in a known location maybe a better solution. > > Assuming a QEMU version has been released that looks for the chain of > GUID-ed structs already, then I think such a change would break > compatibility with that QEMU version. > > If we definitely need a separate spot to include more information in the > flash, for QEMU's parsing, then please introduce a new GUIDed structure, > which contains nothing but a pointer to that spot.
Ah, upon re-reading James's earlier message which he just referenced, namely at https://listman.redhat.com/archives/edk2-devel-archive/2020-November/msg01063.html it's clear that James had already proposed this: > That's not to say we can't have a larger table ... we definitely can, > but it can't be where it is now. we'd have to do something different > like make the table guid describe where the actual table is located > (as a 32 bit offset and length) so as not to break up the 16 bit jump > code. Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#73781): https://edk2.groups.io/g/devel/message/73781 Mute This Topic: https://groups.io/mt/81584577/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
