Andrea Arcangeli wrote: > >> This is arch independent code, I'm surprised mmu_lock is visible here? >> > > The mmu_lock is arch independent as far as I can tell. Pretty much > like the mm->page_table_lock is also independent. All archs will have > some form of shadow pagetables in software or hardware, and mmu_lock > is the lock to take to serialize the pagetable updates and it also > allows to walk the memslots in readonly mode. > >
Well, s390 has everything in hardware, but I suppose they can just ignore the lock. >> What are the new lookup rules? We don't hold mmu_lock everywhere we look >> up a gfn, do we? >> > > It's safe to loop over the memslots by just skipping the ones with > userland_addr == 0 by only holding the mmu_lock. The memslots contents > can't change by holding the mmu_lock. The mmu_lock also serializes the > rmap structures inside the memslot and the spte updates. So by just > taking the mmu_lock it's trivial to do "search memslot", "translate > the hva to its relative rmapp", "find all sptes relative to the hva > and overwrite them with nonpresent-fault". > > But we lookup memslots in parallel in the guest walker and similar places, relying on mmap_sem being taken for read. Maybe we need a rwlock instead, and drop this overloaded usage of mmap_sem. > If the mmu_notifiers would have been registered inside the vma things > would look very different in this area and it might have been possible > to embed the mmu-notifier inside the memslot itself, to avoid the > "search memslot" op. > Nothing guarantees a 1:1 mapping between memslots and vma. You can have a vma backing multiple memslots, or a memslot spanning multiple vmas. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
