linux-kernel - Re: [PATCH 2/2] drm/ttm: Fix vm page protection handling

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Message-ID: <20191203095502.hw3r33ioax2x4kvt@box>
Date:   Tue, 3 Dec 2019 12:55:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        dri-devel@...are.com, pv-drivers@...are.com,
        linux-graphics-maintainer@...are.com,
        Thomas Hellstrom <thellstrom@...are.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH 2/2] drm/ttm: Fix vm page protection handling

On Tue, Dec 03, 2019 at 08:54:46AM +0100, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@...are.com>
> 
> We were using an ugly hack to set the page protection correctly.
> Fix that and instead use vmf_insert_mixed_prot() and / or
> vmf_insert_pfn_prot().
> Also get the default page protection from
> struct vm_area_struct::vm_page_prot rather than using vm_get_page_prot().
> This way we catch modifications done by the vm system for drivers that
> want write-notification.

Hm. Why doesn't your VMA have the right prot flags in the first place? Why
do you need to override them? More context, please.

-- 
 Kirill A. Shutemov