Re: [PATCH 4.4 31/43] mm: fix cache mode tracking in vm_insert_mixed()

[Ben Hutchings]

On Tue, 2018-08-14 at 19:18 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.ÂÂIf anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
> 
> 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.ÂÂAdd 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                Â        Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom