From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932599AbWCPBfe (ORCPT ); Wed, 15 Mar 2006 20:35:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932602AbWCPBfd (ORCPT ); Wed, 15 Mar 2006 20:35:33 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:59150 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S932599AbWCPBfd (ORCPT ); Wed, 15 Mar 2006 20:35:33 -0500 Message-ID: <4418C06D.4050600@vmware.com> Date: Wed, 15 Mar 2006 17:33:33 -0800 From: Zachary Amsden User-Agent: Thunderbird 1.5 (X11/20051201) MIME-Version: 1.0 To: Pavel Machek Cc: Zwane Mwaikambo , Linux Kernel Mailing List Subject: Re: VMI Interface Proposal Documentation for I386, Part 5 References: <4415CE76.9030006@vmware.com> <44167E03.3060807@vmware.com> <20060315234137.GF1919@elf.ucw.cz> In-Reply-To: <20060315234137.GF1919@elf.ucw.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pavel Machek wrote: >> from the hypervisor perspective - if the guest enables interrupts, and >> you have something pending to deliver, for correctness, you have to >> deliver it, right now. But does the kernel truly require that interrupt >> deliver immediately - in most cases, no. In particular, on the fast >> > > I'd say PCI hardware can delay interrupts for any arbitrary > delay... so if driver expects to get them "immediately", I'd say it is > broken. It should be enough to deliver them "soon enough", like not > more than 1msec late... > I agree. One case we hit that did cause us a bug was local APIC delivery of self-IPIs. I didn't dig too deep into why Linux was unhappy without immediate delivery (we deferred delivery here unnecessarily, but did not stop it). I believe this was in SMP specific code that was using self-IPIs to regenerate IRQs . Zach