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

From: Guenter Roeck
Date: Fri Aug 24 2018 - 16:06:12 EST

On Fri, Aug 24, 2018 at 09:17:49PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Aug 24, 2018 at 10:08:28AM -0700, Roland Dreier wrote:
> > > See
> > > <>.
> >
> > Thanks! I'm not using SGI UV and I'm not using kexec, so I guess I
> > sidestepped most of those issues. Greg, I think we need to unrevert
> > the cpa->pfn change (otherwise the L1TF fix probably gets pretty
> > messy) and I guess pull in the other patches that Ben mentions.
> Ok, so what patch should be reverted? I'm seeing other reports of
> problems all around this same area, but I can't figure out exactly what
> to do.
> Guenter, any ideas?
I think we'll need to reapply 87e2bd898d3a ("x86/mm/pat: Ensure cpa->pfn only
contains page frame numbers"), and possibly apply d367cef0a7f0 ("x86/mm/pat:
Fix boot crash when 1GB pages are not supported by the CPU"). Both require
conflict resolutions, but they are quite straightforward. I am not sure
about the other EFI patches.

I am going to send the backports as RFT in a minute. Problem is that I don't
have an EFI system at hand and can not test if this fixes the problem
(or maybe introduces a new one), so someone will need to step in and do
those tests.