[edk2-devel] [PATCH 2/2] UefiCpuPkg: Support 5 level page table in ResetVector

[Ni, Ray]

> 
> But with 5-level paging enabled the reset vector should be able to
> fallback to 4-level paging in case the CPU does not support 5-level
> paging.

The fallback makes sense. Otherwise, forcing to use 5L in an incapable CPU
would be a silent failure because IDT and debug log are not enabled at this
early stage.

Later CpuPei/Dxe module could dump the paging status to tell platform owner
that what level is used in this boot.

With that, that means a 4L reset vector can save 4K space by excluding the PML5 page.
But a 5L reset vector could set CR3 to PML4 page if CPU is incapable.

Thanks,
Ray


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