I think it is OK to always enable 4-level paging at this moment. 5-level paging enabling is NOT super critical for TDX enabling at this moment, as long as we can boot OS kernel. I am fine to enable it later, in a separate patch.
Let's cross the bridge when we come to it. Thank you Yao Jiewen > -----Original Message----- > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Gerd > Hoffmann > Sent: Friday, September 10, 2021 4:20 PM > To: Xu, Min M <min.m...@intel.com> > Cc: Yao, Jiewen <jiewen....@intel.com>; devel@edk2.groups.io; Ard > Biesheuvel <ardb+tianoc...@kernel.org>; Justen, Jordan L > <jordan.l.jus...@intel.com>; Brijesh Singh <brijesh.si...@amd.com>; Erdem > Aktas <erdemak...@google.com>; James Bottomley <j...@linux.ibm.com>; > Tom Lendacky <thomas.lenda...@amd.com> > Subject: Re: [edk2-devel] [PATCH V5 2/2] OvmfPkg/ResetVector: Enable Intel > TDX in ResetVector of Ovmf > > Hi, > > > > If we can use 4-level paging initially, then we surely should go for > > > option (1) > > > and simply not touch the reset vectors paging code. > > > After PoC I find this option is not a good one. Though the reset > > vectors is not touched, there are tricky changes in DxeIpl. To set up > > 5-level paging in an 4-level paging, it should first be switched from > > 64-bit long mode to 32 protected mode, then turn off the Paging, > > disable IA32_ERER.LME, then set the Cr4. The tricky thing is that in > > TDX IA32_EFER is not changeable. MdeModulePkg/.../DxeIpl is widely > > used and it is high risk to make such changes. > > Ok. One more question: Do we have to use 5-level paging at all? > > The only reason I could see is accepting memory with a gpa above 4-level > address space. But with the longer-term plan to support lazy acceptance > (and passing unaccepted memory ranges to the guest kernel) this reason > goes away. > > So I think we could just leave it to the guest kernel to deal with the > switch from 4-level to 5-level paging. Or do I miss something? > > take care, > Gerd > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#80637): https://edk2.groups.io/g/devel/message/80637 Mute This Topic: https://groups.io/mt/85242569/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
