On Thu, 2007-01-11 at 01:49 +0100, Ingo Molnar wrote: > * Rusty Russell <[EMAIL PROTECTED]> wrote: > > > > > - cr3 switches for CONFIG_PARAVIRT syscalls (which are necessary > > > > on x86_64) will probably become very cheap with tagged tlbs > > > > > > but irq overhead is nothing in importance compared to basic syscall > > > overhead. KVM/HVM already runs guest kernel syscalls at native > > > speed. KVM/LL (or Xen) has to switch cr3s to enter guest kernel > > > context > > > > Err no, this isn't true. See Documentation/lhype.txt or various blog > > entries on the subject 8) Both Xen and lhype get native syscall speeds > > (within measurement error). > > i was talking about 64-bit. (we dont really design for 32-bit anymore.)
Oh, ok, because there doesn't seem much point to avoiding using HVM if you're assuming 64 bit, except as an optimization. Full paravirt is more useful for 32-bit, hence lhype started there... > I know that lhype uses Xen's ring 1 trick, but that's a 32-bit-only > thing. Also, can SYSENTER trap from guest userspace ring 3 into guest > kernelspace ring 1 on lhype? As I understand it, sysenter has to go to ring 0, and the reflection cost is way greater than the saving. Rusty. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
