From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [KVM PATCH 1/2] KVM: Directly inject interrupts via irqfd Date: Thu, 22 Oct 2009 17:07:45 +0200 Message-ID: <4AE07541.8060903@redhat.com> References: <20091021143042.14955.22470.stgit@dev.haskins.net> <20091021143453.14955.80578.stgit@dev.haskins.net> <20091021152621.GR29477@redhat.com> <4ADF2A1B.3010205@gmail.com> <20091021153640.GS29477@redhat.com> <4ADF2BDD.40706@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Gregory Haskins , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, alacrityvm-devel@lists.sourceforge.net To: Gregory Haskins Return-path: Received: from mx1.redhat.com ([209.132.183.28]:27500 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755467AbZJVPH4 (ORCPT ); Thu, 22 Oct 2009 11:07:56 -0400 In-Reply-To: <4ADF2BDD.40706@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/21/2009 05:42 PM, Gregory Haskins wrote: > I believe Avi, Michael, et. al. were in agreement with me on that design > choice. I believe the reason is that there is no good way to do EOI/ACK > feedback within the constraints of an eventfd pipe which would be > required for the legacy pin-type interrupts. Therefore, we won't even > bother trying. High-performance subsystems will use irqfd/msi, and > legacy emulation can use the existing injection code (which includes the > necessary feedback for ack/eoi). > > Right. But we don't actually prevent anyone using non-msi with irqfd, which can trigger the bad lock usage from irq context, with a nice boom afterwards. So we need to either prevent it during registration, or to gracefully handle it afterwards. -- error compiling committee.c: too many arguments to function