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

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Message-ID: <20180824200607.GA18715@roeck-us.net>
Date:   Fri, 24 Aug 2018 13:06:07 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Roland Dreier <roland@...estorage.com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        matt@...eblueprint.co.uk, bp@...e.de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>, luto@...nel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>, bp@...en8.de,
        brgerst@...il.com, davej@...emonkey.org.uk, dvlasenk@...hat.com,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        sai.praneeth.prakhya@...el.com, sds@...ho.nsa.gov,
        Thomas Gleixner <tglx@...utronix.de>, toshi.kani@...com,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Yazen.Ghannam@....com
Subject: Re: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only
 contains page frame numbers"

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
> > > <https://lore.kernel.org/lkml/1512686629.18523.217.camel@codethink.co.uk/T/#u>.
> > 
> > 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.

Guenter