Thank you very much, James and Min, for the quick response. I have one small concern on the naming - TdProbeLib. Would it be better if we create a generic CcProbeLib, and just return the CC_GUEST_TYPE? The benefit is that just in case SEV has some usage in the future, we don’t need create SevProbeLib.
BTW: I also propose to change name BaseIoLibIntrinsicSev.inf to BaseIoLibIntrinsicCc.inf. It is very confusing to me, that a Sev.inf include a TdProbeLib. :-( That can be done in a separate patch. Thank you Yao Jiewen > -----Original Message----- > From: [email protected] <[email protected]> On Behalf Of James > Bottomley > Sent: Wednesday, April 13, 2022 8:55 PM > To: Xu, Min M <[email protected]>; [email protected] > Cc: Kinney, Michael D <[email protected]>; Gao, Liming > <[email protected]>; Liu, Zhiguang <[email protected]>; Yao, > Jiewen <[email protected]>; Gerd Hoffmann <[email protected]>; Brijesh > Singh <[email protected]>; Aktas, Erdem <[email protected]>; > Tom Lendacky <[email protected]> > Subject: Re: [edk2-devel] [PATCH 0/4] Introduce TdProbe in MdePkg > > On Wed, 2022-04-13 at 17:08 +0800, Min Xu wrote: > > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3902 > > > > Bad IO performance in SEC phase is observed after TDX features was > > introduced. (after commit b6b2de884864 - "MdePkg: Support mmio for > > Tdx guest in BaseIoLibIntrinsic"). > > > > This is because IsTdxGuest() will be called in each MMIO operation. > > It 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. > > > > TdProbe is introduced in this patch-set. It is called in > > BaseIoLibIntrinsicSev instead of IsTdxGuest. There are 2 versions of > > the TdProbeLib. Null instance of TdProbe always returns TD_PROBE_NON. > > Its OvmfPkg version checks the Ovmf work area to determine the Td > > guest type. > > I tested this out with the TPM code: it restores pretty much all of the > lost performance, thanks! > > Tested-by: James Bottomley <[email protected]> > > James > > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#88868): https://edk2.groups.io/g/devel/message/88868 Mute This Topic: https://groups.io/mt/90436749/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
