> -----Original Message----- > From: kra...@redhat.com <kra...@redhat.com> > Sent: Wednesday, May 10, 2023 3:48 PM > To: devel@edk2.groups.io; Ni, Ray <ray...@intel.com> > Cc: Wu, Jiaxin <jiaxin...@intel.com>; Dong, Eric <eric.d...@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 > > On Wed, May 10, 2023 at 02:48:52AM +0000, Ni, Ray wrote: > > Gerd, > > My understanding is that when code dereferences memory address, the code > itself is responsible for > > supplying the sign-extended linear address. > > The page table creation logic still maps the entire linear memory space > supported by the CPU. > > > > Why do you think covering the half of the space is better? > > edk2 boot services operate on the assumption that everything is identity > mapped, only runtime services know the concept of virtual addresses. > > The lower half of the address space can be identity-mapped (virtual > address == physical address). The upper half can not, so I think it's > better for efi boot services to restrict themself to the lower half.
Good point. I am convinced that 4-level paging only maps up to 2^47 address and 5-level only maps up to 2^56 address. +@Kinney, Michael D, if he have other thoughts. > > take care, > Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#104668): https://edk2.groups.io/g/devel/message/104668 Mute This Topic: https://groups.io/mt/98780500/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/leave/9847357/21656/1706620634/xyzzy [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
