Re: [edk2-devel] [PATCH v2 3/4] OvmfPkg/PlatformPei: rewrite page table calculation

["Laszlo Ersek" <lersek@redhat.com>]

On 2/14/24 10:32, Gerd Hoffmann wrote:
>   Hi,
> 
>> (3) I'm slightly disturbed by the fact that here we don't shift the
>> original MaxAddr by 48 bits, but Level3Pages by 9 bits. Namely, if
>> Level3Pages was set to 1 by the MAX (i.e., because the >> 39 resulted
>> in zero), then the input of *this* bit shift is nonsensical. It's a
>> happenstance that 1 >> 9 is zero too, for Level4Pages, and we're just
>> exploiting that practical result here.
> 
> I had it that way initially.  Got failures for 32-bit builds in CI,
> because the compiler used 64-bit math intrinsics somewhere.

Right, I had certainly expected that in advance. You must have missed my
earlier update on that, still in the v1 thread. My original proposal
there was indeed problematic in that sense, but a few minutes later I
posted an update, replacing the bit-shifts inside the MAX() macro
invocations with RShiftU64() calls:

  Re: [edk2-devel] [PATCH 2/3] OvmfPkg/PlatformPei: rewrite page table calculation
  msgid: 74ccb355-7d71-150b-7258-305149699c0d@redhat.com
  https://edk2.groups.io/g/devel/message/114906

> So I went back to the version working with UINT32 ...

OK.

Laszlo



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