On 17.10.24 18:22, Shakeel Butt wrote:
On Thu, Oct 17, 2024 at 11:17:19AM GMT, David Hildenbrand wrote:
On 16.10.24 20:39, Shakeel Butt wrote:
Ccing couple more folks who are doing similar work (ASI, guest_memfd)
Folks, what is the generic way to check if a given mapping has folios
unmapped from kernel address space?
Can't we just lookup the mapping and refuse these folios that really
shouldn't be looked at?
See gup_fast_folio_allowed() where we refuse secretmem_mapping().
That is exactly what this patch is doing. See [1].
Hah! I should have looked at the full patch not just the discussion
where I was CCed :)
The reason I asked
this question was because I see parallel efforts related to guest_memfd
and ASI are going to unmap folios from direct map. (Yosry already
explained ASI is a bit different). We want a more robust and future
proof solution.
There was a discussion a while ago about having the abstraction of
inaccessible mappings.
See
https://lore.kernel.org/all/c87a4ba0-b9c4-4044-b0c3-c1112601494f@xxxxxxxxxx/
It would be a more future-proof replacement of the secretmem checks.
--
Cheers,
David / dhildenb
