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Date:   Fri, 24 Aug 2018 13:10:25 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Roland Dreier <roland@purestorage.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ben Hutchings <ben.hutchings@codethink.co.uk>,
        LKML <linux-kernel@vger.kernel.org>, stable@vger.kernel.org,
        matt@codeblueprint.co.uk, bp@suse.de,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>, luto@kernel.org,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>, bp@alien8.de,
        brgerst@gmail.com, davej@codemonkey.org.uk, dvlasenk@redhat.com,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        sai.praneeth.prakhya@intel.com, sds@tycho.nsa.gov,
        Thomas Gleixner <tglx@linutronix.de>, toshi.kani@hp.com,
        linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Yazen.Ghannam@amd.com
Subject: Re: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only
 contains page frame numbers"
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On Fri, Aug 24, 2018 at 01:04:09PM -0700, Roland Dreier wrote:
> > 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.
> 
> Are any of those reports public?  If so can you point me at them, I'm
> curious if the symptoms match up.
> 
> I don't think we want to revert anything.  I think you should pull in
> edc3b9129cec and at least the first three patches that Ben listed:
> 
> 21cdb6b56843 x86/mm: Page align the '_end' symbol to avoid pfn conversion bugs
> b61a76f8850d x86/efi: Map RAM into the identity page table for mixed mode
> 753b11ef8e92 x86/efi: Setup separate EFI page tables in kexec paths
> 
> the first patch takes a bit of massaging (mostly because some of it is
> already touched by 02ff2769edbc, which keeps the changes from
> edc3b9129cec, and so we can drop a good bit when applying).  The other
> three apply cleanly.
> 
> I'm currently testing that and can send you the state of my tree in a bit.
> 

Sounds great. I'll hold off with sending my RFT series and wait for your
test results. I think we'll also need d367cef0a7f0c6 ("x86/mm/pat: Fix
boot crash when 1GB pages are not supported by the CPU").

Thanks,
Guenter