I'm using a SEC phase which has a TPM driver to experiment with sorting out measured boot, which is how I noticed (usually SEC doesn't do MMIO) . What I'm seeing is after commit b6b2de884864 ("MdePkg: Support mmio for Tdx guest in BaseIoLibIntrinsic") we get a massive slowdown of about 100x in TPM performance. The reason seems to be this addition to the mmioreadX/mmiowriteX code:
MemoryFence (); - *(volatile UINT16 *)Address = Value; + + if (IsTdxGuest ()) { + TdMmioWrite16 (Address, Value); + } else { + *(volatile UINT16 *)Address = Value; + } + MemoryFence (); The problem is that IsTdxGuest () has this structure: BOOLEAN EFIAPI IsTdxGuest ( VOID ) { if (mTdxProbed) { return mTdxEnabled; } mTdxEnabled = TdIsEnabled (); mTdxProbed = TRUE; return mTdxEnabled; } Which is trying to cache the result of the probe in the efi data segment. However, that doesn't work in SEC, because the data segment is read only (so the write seems to succeed but a read will always return the original value), leading to us calling TdIsEnabled() check for every mmio we do, which is causing the slowdown because it's very expensive. James -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#88800): https://edk2.groups.io/g/devel/message/88800 Mute This Topic: https://groups.io/mt/90427994/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-