From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] KVM: Use IRQF_ONESHOT for assigned device MSI interrupts Date: Mon, 04 Jun 2012 15:16:33 +0200 Message-ID: <4FCCB531.4000008@siemens.com> References: <20120601161521.26935.25606.stgit@bling.home> <4FC8F042.5050600@siemens.com> <1338570192.23475.25.camel@bling.home> <4FC8F867.7080103@siemens.com> <1338573558.23475.41.camel@bling.home> <4FC90961.8030701@siemens.com> <4FCB2359.9020505@redhat.com> <4FCC9EAC.9090007@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Alex Williamson , "kvm@vger.kernel.org" , "mtosatti@redhat.com" , "linux-kernel@vger.kernel.org" , "yongjie.ren@intel.com" To: Thomas Gleixner Return-path: Received: from david.siemens.de ([192.35.17.14]:26214 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756884Ab2FDNQl (ORCPT ); Mon, 4 Jun 2012 09:16:41 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 2012-06-04 15:07, Thomas Gleixner wrote: > On Mon, 4 Jun 2012, Jan Kiszka wrote: >> On 2012-06-04 13:21, Thomas Gleixner wrote: >> So this shortcut requires some checks before being applied to a specific >> MSI/MSI-X vector. >> >> >> Taking KVM aside, my general question remains if threaded MSI handlers >> of all devices really need to apply IRQF_ONESHOT though they should have >> no use for it. > > In theory no, but we had more than one incident, where threaded irqs > w/o a primary handler and w/o IRQF_ONEHSOT lead to full system > starvation. Linus requested this sanity check and I think it's sane > and required. OK. > > In fact it's a non issue for MSI. MSI uses handle_edge_irq which does > not mask the interrupt. IRQF_ONESHOT is a noop for that flow handler. Isn't irq_finalize_oneshot processes for all flows? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux