linux-kernel - Re: [PATCH] mm/migrate: properly preserve write attribute in special migrate entry

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Message-Id: <20180403164522.657185a44e8ada1b741f0a9e@linux-foundation.org>
Date:   Tue, 3 Apr 2018 16:45:22 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Ralph Campbell <rcampbell@...dia.com>
Subject: Re: [PATCH] mm/migrate: properly preserve write attribute in
 special migrate entry

On Tue, 3 Apr 2018 19:03:36 -0400 Jerome Glisse <jglisse@...hat.com> wrote:

> > That sounds a bit serious.  Was a -stable backport considered?
> 
> Like discuss previously with Michal, for lack of upstream user yet
> (and PowerPC users of this code are not upstream either yet AFAIK).
> 
> Once i get HMM inside nouveau upstream, i will evaluate if people
> wants all fixes to be back ported to stable.
> 
> Finaly this one isn't too bad, it just burn CPU cycles by forcing
> CPU to take a second fault on write access ie double fault the same
> address. There is no corruption or incorrect states (it behave as
> a COWed page from a fork with a mapcount of 1).

OK, I updated the changelog with this info.

> Do you still want me to be more aggressive with stable backport ?
> I don't mind either way. I expect to get HMM nouveau upstream over
> next couple release cycle.

I guess that doing a single, better-organized cherrypick at a suitable
time in the future is a good approach.  You might want to discuss this
plan with Greg before committing too far.