Re: [edk2-devel] [PATCH V7 1/1] OvmfPkg: Enable TDX in ResetVector

["Yao, Jiewen" <jiewen.yao@intel.com>]

I recommend we start with 2 metadata and check in.
It is working today for both SEV and TDX, with KVM and Cloud Hypervisor support.

Thank you
Yao Jiewen

> -----Original Message-----
> From: Xu, Min M <min.m.xu@intel.com>
> Sent: Sunday, September 26, 2021 7:17 AM
> To: devel@edk2.groups.io; brijesh.singh@amd.com
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>; Justen, Jordan L
> <jordan.l.justen@intel.com>; Gerd Hoffmann <kraxel@redhat.com>; Erdem
> Aktas <erdemaktas@google.com>; James Bottomley <jejb@linux.ibm.com>;
> Yao, Jiewen <jiewen.yao@intel.com>; Tom Lendacky
> <thomas.lendacky@amd.com>
> Subject: RE: [edk2-devel] [PATCH V7 1/1] OvmfPkg: Enable TDX in ResetVector
> 
> On September 25, 2021 11:21 AM, Brijesh Singh wrote:
> > Hi Min,
> >
> >
> > On 9/24/21 7:03 PM, Xu, Min M wrote:
> > > On September 24, 2021 6:58 PM, Brijesh Singh wrote:
> > >> Hi Min,
> > >>
> > >> On 9/21/21 4:05 AM, Min Xu wrote:
> > >>>  ;
> > >>>  ; Modified:  EAX, EBX, ECX, EDX
> > >>>  ;
> > >>>  SetCr3ForPageTables64:
> > >>> -
> > >>> -    ; Clear the WorkArea header. The SEV probe routines will populate the
> > >>> -    ; work area when detected.
> > >>> -    mov     byte[WORK_AREA_GUEST_TYPE], 0
> > >> Why you are removing the above block ? The workarea hdr must be
> > >> initialized to zero, its not safe to assume that the guest memory is
> > >> zero'ed in the non- encrypted case.
> > >>
> > > Hi, Brijesh
> > > Please see below explanation (It is in the commit message)
> > > - In Main16 entry point, after TransitionFromReal16To32BitFlat,
> > >    WORK_AREA_GUEST_TYPE is cleared to 0. WORK_AREA_GUEST_TYPE was
> > >    previously cleared in SetCr3ForPageTables64 (see commit ab77b60).
> > >    This doesn't work after TDX is introduced in Ovmf. It is because all
> > >    TDX CPUs (BSP and APs) start to run from 0xfffffff0. In previous code
> > >    WORK_AREA_GUEST_TYPE will be cleared multi-times in TDX guest. So for
> > >    SEV and Legacy guest it is moved to Main16 entry point (after
> > >    TransitionFromReal16To32BitFlat). For TDX guest
> > WORK_AREA_GUEST_TYPE
> > >    is cleared and set in InitTdxWorkarea
> >
> > thanks for clarifying it.
> >
> > This is very busy commit and making several changes at once, so some of
> > important common code movement is getting lost. Maybe I recommend you
> to
> > please break it into multiple. e,g  this particular change can be very easily
> broken
> > into two commits
> >
> > 1) Since TDX support need the change in the boot flow, and you are no longer
> > using the Main.asm from the UefiCpuPkg. This can be a pre-patch in which you
> > copy UefiCpuPkg/ResetVector/Vtf0/main.asm ->
> > OvmfPkg/ResetVector/Main.asm and document reason behind the move.
> >
> > 2) Remove clearing of workarea from SetCr3ForPageTables64 to Main.asm
> >
> > Now that we have override for the Main.asm, I think clearing of the workarea
> > should be done for all architecture (Ia32, x64) to cover the cases where
> > someone builds the OVMF for 32bit or IA32 and X64.
> >
> Thanks for reminder. I have updated the patch-set as you mentioned. But I am
> waiting for a conclusion of the Metadata, a unified metadata or two separate
> metadata.
> 
> Hoffmann and Jiewen
> Do we have a conclusion?
> 
> Thanks
> Min