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From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Dun Tan <dun.tan@intel.com>
Cc: devel@edk2.groups.io, Ray Ni <ray.ni@intel.com>,
	 Laszlo Ersek <lersek@redhat.com>,
	Rahul Kumar <rahul1.kumar@intel.com>
Subject: Re: [edk2-devel] [PATCH] UefiCpuPkg:Limit PhysicalAddressBits in speicial case
Date: Wed, 10 Jan 2024 11:54:30 +0100	[thread overview]
Message-ID: <c7ahft27s5rozrirr3mdlzfdc7gfid2qaaf4c3iwhcn6x4czsy@3hiex4wsjftd> (raw)
In-Reply-To: <20240110080544.1350-1-dun.tan@intel.com>

On Wed, Jan 10, 2024 at 04:05:44PM +0800, Dun Tan wrote:
> When creating smm page table, limit maximum
> supported physical address bits returned by
> CalculateMaximumSupportAddress() to 48 if
> 5-Level Paging is disabled.
> When 5-Level Paging is disabled and the
> PhysicalAddressBits retrived from CPU HOB or
> CpuId is bigger than 48, only [0, 2^48 -1]
> range in 52-bit physical address is mapped
> in page table.

I think this is wrong.  Virtual addresses are sign-extended,
i.e. the virtual address space without 5-level paging is:

 0x0000000000000000 -> 0x00007fffffffffff and
 0xffff800000000000 -> 0xffffffffffffffff

Therefore identity-mapping works for [0, 2^47-1] only.

take care,
  Gerd



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  parent reply	other threads:[~2024-01-10 10:54 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-10  8:05 [edk2-devel] [PATCH] UefiCpuPkg:Limit PhysicalAddressBits in speicial case duntan
2024-01-10  9:08 ` Ni, Ray
2024-01-10 10:54 ` Gerd Hoffmann [this message]
2024-01-10 12:19   ` Laszlo Ersek
2024-01-11  1:56   ` duntan

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