linux-kernel - Re: [PATCH 4.4 31/43] mm: fix cache mode tracking in vm_insert

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Message-ID: <1536339923.3024.112.camel@codethink.co.uk>
Date:   Fri, 07 Sep 2018 18:05:23 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 4.4 31/43] mm: fix cache mode tracking in
 vm_insert_mixed()

On Tue, 2018-08-14 at 19:18 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dan Williams <dan.j.williams@...el.com>
> 
> commit 87744ab3832b83ba71b931f86f9cfdb000d07da5 upstream
> 
> vm_insert_mixed() unlike vm_insert_pfn_prot() and vmf_insert_pfn_pmd(),
> fails to check the pgprot_t it uses for the mapping against the one
> recorded in the memtype tracking tree.  Add the missing call to
> track_pfn_insert() to preclude cases where incompatible aliased mappings
> are established for a given physical address range.
[...]

This apparently breaks a number of DRM drivers.  The upstream fixes
are:

8ef4227615e1 x86/io: add interface to reserve io memtype for a resource range. (v1.1)
7cf321d118a8 drm/drivers: add support for using the arch wc mapping API.

They appear to apply cleanly to 4.4-stable.  They are included in 4.9
so no other stable branch needs them.

Ben.

-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom