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

[Greg Kroah-Hartman]

On Wed, Aug 22, 2018 at 05:48:32PM -0700, Roland Dreier wrote:
> 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?

I tried to dig through my old emails, but could not find anything,
sorry.

> 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
> addresses.
> 
> 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.

Ugh, not good.

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

I can try to add it back and see what blows up, want me to attempt that?
:)

thanks,

greg k-h