On Wed, Mar 24, 2021 at 02:35:38PM +0100, Thomas Hellström (Intel) wrote:
We are trying to make a sensible driver API to deal with huge pages.In an ideal world the creation/destruction of page table levels wouldHmm, but I'm not sure what problem we're trying to solve by changing the
by dynamic at this point, like THP.
interface in this way?
Currently if the core vm requests a huge pud, we give it one, and if weWell, my thought would be to move the pte related stuff into
can't or don't want to (because of dirty-tracking, for example, which is
always done on 4K page-level) we just return VM_FAULT_FALLBACK, and the
fault is retried at a lower level.
vmf_insert_range instead of recursing back via VM_FAULT_FALLBACK.
I don't know if the locking works out, but it feels cleaner that the
driver tells the vmf how big a page it can stuff in, not the vm
telling the driver to stuff in a certain size page which it might not
want to do.
Some devices want to work on a in-between page size like 64k so they
can't form 2M pages but they can stuff 64k of 4K pages in a batch on
every fault.
That idea doesn't fit naturally if the VM is driving the size.
Jason