Hi Gerd,
Could you share me which document introduce the sign-extended impact the line
address width?
Thanks,
Jiaxin
> -----Original Message-----
> From: Gerd Hoffmann <kra...@redhat.com>
> Sent: Tuesday, May 9, 2023 10:39 PM
> To: devel@edk2.groups.io; Wu, Jiaxin <jiaxin...@intel.com>
> Cc: Dong, Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; Zeng, Star
> <star.z...@intel.com>; Kumar, Rahul R <rahul.r.ku...@intel.com>
> Subject: Re: [edk2-devel] [PATCH v1 1/3] UefiCpuPkg/SecCore: Migrate page
> table to permanent memory
>
> Hi,
>
> > + if (PagingMode == Paging4Level1GB || PagingMode == Paging4Level) {
> > + //
> > + // The max lineaddress bits is 48 for 4 level page table.
> > + //
> > + VirPhyAddressSize.Bits.PhysicalAddressBits = MIN
> (VirPhyAddressSize.Bits.PhysicalAddressBits, 48);
> > + }
>
> virtual addresses in long mode are sign-extended. Which means you have
> only 47 bits (or 56 bits with 5-level paging) for identity mappings.
>
> take care,
> Gerd
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