From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] KVM: Improve interrupt response Date: Tue, 2 Jan 2007 12:12:56 +0100 Message-ID: <20070102111256.GA27541@elte.hu> References: <20061231132232.A98E92500F7@il.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, akpm-3NddpPZAyC0@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Return-path: To: Avi Kivity Content-Disposition: inline In-Reply-To: <20061231132232.A98E92500F7-LjA0eNSCdXrQnzwC+xcbyw@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: > From: Dor Laor > > The current interrupt injection mechanism might delay an interrupt > under the following circumstances: > > - if injection fails because the guest is not interruptible (rflags.IF clear, > or after a 'mov ss' or 'sti' instruction). Userspace can check rflags, > but the other cases or not testable under the current API. > - if injection fails because of a fault during delivery. This probably > never happens under normal guests. > - if injection fails due to a physical interrupt causing a vmexit so that > it can be handled by the host. > > in all cases the guest proceeds without processing the interrupt, > reducing the interactive feel and interrupt throughput of the guest. > > This patch fixes the situation by allowing userspace to request an > exit when the 'interrupt window' opens, so that it can re-inject the > interrupt at the right time. Guest interactivity is very visibly > improved. Andrew, i'd argue for this to be included in v2.6.20, because it's an obvious bugfix. I've tested this patch and it's included in current -rt and i saw no regressions. Acked-by: Ingo Molnar 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