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

[Christian KÃnig]

Am 03.12.19 um 10:55 schrieb Kirill A. Shutemov:
> On Tue, Dec 03, 2019 at 08:54:46AM +0100, Thomas HellstrÃm (VMware) wrote:
> > From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
> >
> > 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.

TTM allows for graphics buffer to move between system and IO memory. So 
the prot flags can change on the fly for a VMA.

Regards,
Christian.