On 3/1/21 9:32 AM, Daniel Vetter wrote:
On Wed, Jan 06, 2021 at 10:01:09PM -0500, Felix Kuehling wrote:
From: Philip Yang <Philip.Yang@xxxxxxx>
Register vram memory as MEMORY_DEVICE_PRIVATE type resource, to
allocate vram backing pages for page migration.
Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
So maybe I'm getting this all wrong, but I think that the current ttm
fault code relies on devmap pte entries (especially for hugepte entries)
to stop get_user_pages. But this only works if the pte happens to not
point at a range with devmap pages.
I don't think that's in TTM yet, but the proposed fix, yes (see email I
just sent in another thread),
but only for huge ptes.
This patch here changes that, and so probably breaks this devmap pte hack
ttm is using?
If I'm not wrong here then I think we need to first fix up the ttm code to
not use the devmap hack anymore, before a ttm based driver can register a
dev_pagemap. Also adding Thomas since that just came up in another
discussion.
It doesn't break the ttm devmap hack per se, but it indeed allows gup to
the range registered, but here's where my lack of understanding why we
can't allow gup-ing TTM ptes if there indeed is a backing struct-page?
Because registering MEMORY_DEVICE_PRIVATE implies that, right?
/Thomas
-Daniel
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