From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Nakajima, Jun" Subject: Re: QEMU PIC indirection patch for in-kernel APIC work Date: Wed, 4 Apr 2007 08:36:04 -0700 Message-ID: <8FFF7E42E93CC646B632AB40643802A8025B9580@scsmsx412.amr.corp.intel.com> References: <4613BF07.50606@qumranet.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: "Avi Kivity" , "Anthony Liguori" Return-path: Content-class: urn:content-classes:message In-Reply-To: <4613BF07.50606-atKUWr5tajBWk0Htik3J/w@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 Avi Kivity wrote: > Anthony Liguori wrote: >> Avi Kivity wrote: >>> Anthony Liguori wrote: >>>> >>>> Then again, are we really positive that we have to move the APIC >>>> into the kernel? A lot of things will get much more complicated. >>> >>> The following arguments are in favor: >>> - allow in-kernel paravirt drivers to interrupt the guest without >>> going through qemu (which involves a signal and some complexity) >>> - same for guest SMP IPI >>> - reduced overhead for a much-loved hardware component (especially >>> on Windows, where one regularly sees 100K apic updates a second) >> >> This is for the TPR right? VT has special logic to handle TPR >> virtualization doesn't it? I thought SVM did too... >> > > Yes, the TPR. Both VT and SVM virtualize CR8 in 64-bit mode. SVM > also supports CR8 in 32-bit mode through a nwe instruction encoding, > but > nobody uses that to my knowledge. Maybe some brave soul can hack kvm > to patch the new instruction in place of the mmio instruction Windows > uses > to bang on the tpr. Actually VT has virtual TPR support that does not require CR8. We submitted a patch for Xen. Please see http://lists.xensource.com/archives/html/xen-devel/2007-03/msg00993.html The spec should be available soon. We are working on a patch for KVM. Jun --- Intel Open Source Technology Center ------------------------------------------------------------------------- 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