From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: Paravirt KVM capabilities Date: Thu, 11 Jan 2007 01:49:57 +0100 Message-ID: <20070111004957.GA3279@elte.hu> References: <20070109141916.GA13276@vlad.carfax.org.uk> <45A3A642.1030604@qumranet.com> <1168384852.19646.161.camel@localhost.localdomain> <20070110094750.GA934@elte.hu> <45A4BB74.9010102@redhat.com> <20070110101839.GA6444@elte.hu> <45A4C345.5050404@qumranet.com> <20070110105202.GA13412@elte.hu> <1168476120.19646.209.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: To: Rusty Russell Content-Disposition: inline In-Reply-To: <1168476120.19646.209.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org * Rusty Russell 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.) 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? Ingo ------------------------------------------------------------------------- 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