From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Remaining passthrough/VT-d tasks list Date: Sat, 27 Sep 2008 12:49:31 +0300 Message-ID: <48DE01AB.2050303@redhat.com> References: <0122C7C995D32147B66BF4F440D3016301C49E61@pdsmsx415.ccr.corp.intel.com> <200809241431.13571.sheng.yang@intel.com> <48D9FC8B.2040902@redhat.com> <200809271715.54439.sheng.yang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Han, Weidong" , "kvm@vger.kernel.org" , Amit Shah , "benami@il.ibm.com" , "muli@il.ibm.com" , "Kay, Allen M" , "Zhang, Xiantao" To: "Yang, Sheng" Return-path: Received: from mx2.redhat.com ([66.187.237.31]:54976 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751878AbYI0Jtu (ORCPT ); Sat, 27 Sep 2008 05:49:50 -0400 In-Reply-To: <200809271715.54439.sheng.yang@intel.com> Sender: kvm-owner@vger.kernel.org List-ID: Yang, Sheng wrote: > After check host shared interrupts situation, I got a question here: > > If I understand correctly, current solution don't block host shared irq, just > come with the performance pentry. The penalty come with host disabled irq > line for a period. We have to wait guest to write EOI. But I fail to see the > correctness problem here (except a lot of spurious interrupt in the guest). > > I've checked mail, but can't find clue about that. Can you explain the > situation? > > If the guest fails to disable interrupts on a device that shares an interrupt line with the host, the host will experience an interrupt flood. Eventually the host will disable the host device as well. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.