Re: [patch 01/13] x86/mm: get_user_pages_fast_atomic

Avi Kivity
2008-09-07T08:42:20Z

Marcelo Tosatti wrote:
> From: Nick Piggin <nickpiggin@yahoo.com.au>
>
> Provide a lockless pagetable walk function without fallback to mmap_sem
> on error.
>

I would like to avoid this if possible. Not only is this a change to
the core (with backporting headaches), if we resync in atomic context
this can mean a long time spent with preemption disabled.

We might get around the need by dropping the lock when we resync, fetch
the gfns without the lock, and after reacquiring it check whether we can
proceed or whether we need to abort and let the guest retry. We can
probably proceed unless one of two things have happened: an mmu page was
zapped, or out page was oos'ed while we were resyncing it.

--
error compiling committee.c: too many arguments to function