From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: QEMU PIC indirection patch for in-kernel APIC work Date: Wed, 4 Apr 2007 23:21:03 +0200 Message-ID: <20070404212103.GA19026@elte.hu> References: <4613B438.60107@codemonkey.ws> <4613B89F.8090806@qumranet.com> <4613BC6B.1070708@codemonkey.ws> <4613BF07.50606@qumranet.com> <4613C993.9020405@codemonkey.ws> <4613CC01.1090500@qumranet.com> <4613CDB2.4000903@codemonkey.ws> <4613D001.3040606@qumranet.com> <20070404200112.GA6070@elte.hu> <4614098F.2030307@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <4614098F.2030307-r/Jw6+rmf7HQT0dZR+AlfA@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 * Anthony Liguori wrote: > But why is it a good thing to do PV drivers in the kernel? You lose > flexibility and functionality to gain performance. [...] in Linux a kernel-space network driver can still be tunneled over user-space code, and hence you can add arbitrary add-on functionality (and thus have flexibility), without slowing down the common case (which would be to tunnel the guest's network traffic into the firewall rules of the kernel. No need to touch user-space for any of that). if performance didnt matter and if it were all about flexibility then Bochs/Qemu could have migrated most Windows users to Linux 10 years ago. The reality is, performance and precision of emulation very much matters. 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