Andrea Arcangeli wrote: > On Thu, Jan 24, 2008 at 07:56:43AM +0200, Avi Kivity wrote: > >> What I need is a list of (mm, va) that map the page. kvm doesn't have >> access to that, export notifiers do. It seems reasonable that export >> notifier do that rmap walk since they are part of core mm, not kvm. >> > > Yes. Like said in earlier email we could ignore the slowdown and > duplicate the mm/rmap.c code inside kvm, but that looks a bad layering > violation and it's unnecessary, dirty and suboptimal IMHO. > >
Historical note: old kvm versions (like the what will eventually ship in 2.6.24) have a page-based rmap (hooking the rmap list off page->private). We changed that to an mm based rmap since page->private is not available when kvm maps general userspace memory. >> Alternatively, kvm can change its internal rmap structure to be page based >> instead of (mm, hva) based. The problem here is to size this thing, as we >> don't know in advance (when the kvm module is loaded) whether 0% or 100% >> (or some value in between) of system memory will be used for kvm. >> > > Another issue is that for things like the page sharing driver, it's > more convenient to be able to know exactly which "sptes" belongs to a > certain userland mapping, and only that userland mapping (not all > others mappings of the physical page). So if the rmap becomes page > based, it'd be nice to still be able to find the "mm" associated with > that certain spte pointer to skip all sptes in the other "mm" during > the invalidate. > You also need the mm (or rather, the kvm structure, but they have a 1:1 relationship) to be able to lock and maintain the shadow structures properly. -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- 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
