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

["Gerd Hoffmann" <kraxel@redhat.com>]

On Wed, Feb 14, 2024 at 11:48:57AM +0100, Laszlo Ersek wrote:
> 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:

Happened even with the RShiftU64() calls, must have been something else.

take care,
  Gerd



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#115443): https://edk2.groups.io/g/devel/message/115443
Mute This Topic: https://groups.io/mt/104117101/7686176
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io]
-=-=-=-=-=-=-=-=-=-=-=-