linux-kernel - Re: [PATCH v2] mm: Track page table modifications in __apply_to_page

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Date:   Sat, 22 Aug 2020 23:25:41 +0200
From:   Pavel Machek <pavel@....cz>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <joro@...tes.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Airlie <airlied@...hat.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Vrabel <david.vrabel@...rix.com>,
        Joerg Roedel <jroedel@...e.de>, stable@...r.kernel.org
Subject: Re: [PATCH v2] mm: Track page table modifications in
 __apply_to_page_range()

Hi!
> > > 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.
> 
> The impact appears limited to x86-32, where apply_to_page_range may miss
> updating the PMD. That leads to explosions in drivers like

Is this alone supposed to fix my problems with graphics on Thinkpad
X60? Let me try...

Best regards,
								Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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