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

From: Christian KÃnig
Date: Tue Dec 03 2019 - 04:58:24 EST


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.