linux-kernel - Re: [PATCH 4.9] x86/pti/efi: broken conversion from efi to kernel page table

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Date:   Fri, 12 Jan 2018 15:27:32 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
cc:     steven.sistare@...cle.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, gregkh@...uxfoundation.org, jkosina@...e.cz,
        hughd@...gle.com, dave.hansen@...ux.intel.com, luto@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [PATCH 4.9] x86/pti/efi: broken conversion from efi to kernel
 page table

On Thu, 11 Jan 2018, Pavel Tatashin wrote:

> The page table order must be increased for EFI table in order to avoid a
> bug where NMI tries to change the page table to kernel page table, while
> efi page table is active.
> 
> For more disccussion about this bug, see this thread:
> http://lkml.iu.edu/hypermail/linux/kernel/1801.1/00951.html
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> Reviewed-by: Steven Sistare <steven.sistare@...cle.com>

Acked-by: Jiri Kosina <jkosina@...e.cz>

We are carrying similar patch in our 4.4 codestream as well.

Please note that this is needed only for those trees that have 67a9108ed43 
("x86/efi: Build our own page table structures") backported to it. That 
used to be in some -stable releases, and some had it reverted, so please 
check that.

-- 
Jiri Kosina
SUSE Labs