[edk2-devel] [PATCH V6 33/42] OvmfPkg: Update PlatformInitLib for Tdx guest to publish ram regions
Yao, Jiewen
jiewen.yao at intel.com
Wed Feb 23 10:49:08 UTC 2022
I think both are correct.
The dump info is from a *client* machine in old generation - kabylake. 39 bits physical is good enough.
GPAW in TD is enforced by TDX-module. Please refer to
https://www.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1.0-public-spec-v0.931.pdf,
Section 10.1.2, Table 10.1 - RBX[5:0] is GPAW - only 48 and 52 are possible.
Thank you
Yao Jiewen
> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Gerd
> Hoffmann
> Sent: Wednesday, February 23, 2022 6:07 PM
> To: Xu, Min M <min.m.xu at intel.com>
> Cc: devel at edk2.groups.io; Ard Biesheuvel <ardb+tianocore at kernel.org>; Justen,
> Jordan L <jordan.l.justen at intel.com>; Brijesh Singh <brijesh.singh at amd.com>;
> Aktas, Erdem <erdemaktas at google.com>; James Bottomley
> <jejb at linux.ibm.com>; Yao, Jiewen <jiewen.yao at intel.com>; Tom Lendacky
> <thomas.lendacky at amd.com>
> Subject: Re: [edk2-devel] [PATCH V6 33/42] OvmfPkg: Update PlatformInitLib
> for Tdx guest to publish ram regions
>
> Hi,
>
> > Another update is in PlatformAddressWidthInitialization. The physical
> > address width that Tdx guest supports is either 48 or 52.
>
> Hmm. Sure this is correct?
>
> 48 is the max _virtual_ address space possible with 4-level paging.
> The _physical_ address space might be much smaller, like this
> (kaby lake desktop system):
>
> # lscpu
> Architecture: x86_64
> CPU op-mode(s): 32-bit, 64-bit
> Address sizes: 39 bits physical, 48 bits virtual
> Byte Order: Little Endian
>
> Maybe all TDX-capable Intel CPUs actually have >= 48 bits physical,
> so this could be fine, but please double-check.
>
> thanks,
> Gerd
>
>
>
>
>
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