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

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Message-ID: <20180113131623.GA21957@kroah.com>
Date:   Sat, 13 Jan 2018 14:16:23 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Pavel Tatashin <pasha.tatashin@...cle.com>,
        steven.sistare@...cle.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.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 Fri, Jan 12, 2018 at 03:27:32PM +0100, Jiri Kosina wrote:
> 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.

The 4.4-stable tree reverted this patch, so I'll take the 4.4-specific
patch for this that was just sent.

thanks,

greg k-h