On Tue, Jan 29, 2008 at 07:19:18PM +0100, Joerg Roedel wrote: > Since NPT uses the host page table format it is in theory possible to > add the pagetable to the Linux MM rmap. In this case it would not be > necessary to use MMU notifiers. But I think this would complicate the > NPT support code significantly.
The Linux rmap isn't like Christoph's secondary-rmap, nor similar to the KVM rmap. The difference is that the linux rmap requires zero ram in rmap structures, for each new page allocated by a linux page fault. While KVM rmap requires a few bytes for each new page allocated with get_user_pages and mapped/cached in some spte. So we can't represent NTP pagetables in linux rmap and the current mmu notifier model is quite optimal for it. What instead may be possible with NTP given the radix tree format, is to make a KVM rmap implementation for NPT similar to the one in the linux VM, to avoid losing 64bit of ram for each new NPT pagetable allocated and mapped, so the mmu notifier may be able to reverse from host virtual to NPT pagetable without having to use any metadata but by just walking the NPT tree for the VM. I'm not sure if it's feasible though. ------------------------------------------------------------------------- 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
