Re: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only contains page frame numbers"

From: Roland Dreier
Date: Wed Aug 22 2018 - 20:48:50 EST

On Fri, Dec 15, 2017 at 2:20 AM Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> This reverts commit 87e2bd898d3a79a8c609f183180adac47879a2a4 which is
> commit edc3b9129cecd0f0857112136f5b8b1bc1d45918 upstream.
> Turns there was too many other issues with this patch to make it viable
> for the stable tree.

This was sort of a long time ago, but does anyone remember why this
needed to be reverted from 4.4?

The reason I ask is that without this, commit 02ff2769edbc /
"x86/mm/pat: Make set_memory_np() L1TF safe" in 4.4.148 is broken.
That patch has

- set_pud(pud, __pud(cpa->pfn | _PAGE_PSE |
- massage_pgprot(pud_pgprot)));
+ set_pud(pud, pud_mkhuge(pfn_pud(cpa->pfn,
+ canon_pgprot(pud_pgprot))));

(and similarly for pmds) but pfn_pud() is operating on page frame
numbers and __pud(cpa->pfn... in the old code is operating on physical

This is bad enough that 4.4.148 and all newer 4.4.y crash early in
boot on some EFI systems that I have.

For now I am re-applying the "ensure cpa->pfn only contains page frame
numbers" patch, ported on top of 4.4.151.

- R.