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Date:   Fri, 21 Aug 2020 13:35:48 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Joerg Roedel <joro@8bytes.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Chris Wilson <chris@chris-wilson.co.uk>,
        intel-gfx@lists.freedesktop.org, Pavel Machek <pavel@ucw.cz>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Dave Airlie <airlied@redhat.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Vrabel <david.vrabel@citrix.com>,
        Joerg Roedel <jroedel@suse.de>, stable@vger.kernel.org
Subject: Re: [PATCH v2] mm: Track page table modifications in
 __apply_to_page_range()
Message-Id: <20200821133548.be58a3b0881b41a32759fa04@linux-foundation.org>
In-Reply-To: <20200821123746.16904-1-joro@8bytes.org>
References: <20200821123746.16904-1-joro@8bytes.org>
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On Fri, 21 Aug 2020 14:37:46 +0200 Joerg Roedel <joro@8bytes.org> wrote:

> The __apply_to_page_range() function is also used to change and/or
> allocate page-table pages in the vmalloc area of the address space.
> Make sure these changes get synchronized to other page-tables in the
> system by calling arch_sync_kernel_mappings() when necessary.

There's no description here of the user-visible effects of the bug. 
Please always provide this, especially when proposing a -stable
backport.  Take pity upon all the downstream kernel maintainers who are
staring at this wondering whether they should risk adding it to their
kernels.