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Date: Tue, 9 May 2023 16:39:07 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: devel@edk2.groups.io, jiaxin.wu@intel.com
Cc: Eric Dong <eric.dong@intel.com>, Ray Ni <ray.ni@intel.com>, 
	Zeng Star <star.zeng@intel.com>, Rahul Kumar <rahul1.kumar@intel.com>
Subject: Re: [edk2-devel] [PATCH v1 1/3] UefiCpuPkg/SecCore: Migrate page table to permanent memory
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References: <20230509102253.16632-1-jiaxin.wu@intel.com>
 <20230509102253.16632-2-jiaxin.wu@intel.com>
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  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