Re: [edk2-devel] [PATCH v1 1/3] UefiCpuPkg/SecCore: Migrate page table to permanent memory

["Wu, Jiaxin" <jiaxin.wu@intel.com>]

Hi Gerd,

Could you share me which document introduce the sign-extended impact the line address width?

Thanks,
Jiaxin 

> -----Original Message-----
> From: Gerd Hoffmann <kraxel@redhat.com>
> Sent: Tuesday, May 9, 2023 10:39 PM
> To: devel@edk2.groups.io; Wu, Jiaxin <jiaxin.wu@intel.com>
> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Zeng, Star
> <star.zeng@intel.com>; Kumar, Rahul R <rahul.r.kumar@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