On 06/08/21 14:27, Xu, Min M wrote: > On 06/04/2021 12:12 AM, Laszlo wrote:
>> But it counts as an absolute disaster nowadays, and should not be revived in >> any platform. If you don't have pflash in TDX guests, just accept that you >> won't have non-volatile variables. And link PlatformFvbLibNull into >> EmuVariableFvbRuntimeDxe. You're going to need a separate >> PlatformBootManagerLib instance anyway. >> > I have a question here, that if PlatformFvbLibNull is linked into > EmuVaiableFvRuntimeDxe, > Does it mean it cannot write to the in-RAM variable store? No, that's not the case; PlatformFvbLibNull only turns the hooks (special callbacks) into no-ops; the normal operation of EmuVariableFvbRuntimeDxe is not disrupted. The APIs in the PlatformFvbLib class are PlatformFvbDataRead, PlatformFvbDataWritten, PlatformFvbBlocksErased; they are called at the ends of the functions FvbProtocolEraseBlocks(), FvbProtocolWrite(), FvbProtocolRead(), in "OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.c". If the PlatformFvb* APIs do nothing, that's not a problem for EmuVariableFvbRuntimeDxe. (In fact, even in the non-Null instance -- that is, in the EmuVariableFvbLib instance --, the read and erase callbacks are empty; and the write callback only signals an event, at best.) >> (We should have removed EmuVariableFvbRuntimeDxe a long time ago from >> the traditional OVMF platforms, i.e. made pflash a hard requirement, even >> when SMM is not built into the platform -- but whenever I tried that, Jordan >> always shot me down.) >> > I am afraid in TDVF we have to use EmuVariableFvRuntimeDxe to emulate the > in-RAM, as I explained pflash is not part of the *board* in TDX setup. Using EmuVariableFvbRuntimeDxe in the TDVF platform is fine (with the Null hooks, see above), as long as we carefully document the expected / resultant behavior of the UEFI variable services. (This is not a comment on my part on the SB situation, which remains an open question for TDVF, for the time being.) Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#76224): https://edk2.groups.io/g/devel/message/76224 Mute This Topic: https://groups.io/mt/83283616/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-