From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v3 0/2] kvm: level irqfd and new eoifd Date: Wed, 11 Jul 2012 12:18:15 +0200 Message-ID: <4FFD52E7.3030806@siemens.com> References: <20120703191106.6735.78272.stgit@bling.home> <4FFD4D0A.2000202@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Alex Williamson , "mst@redhat.com" , "gleb@redhat.com" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Avi Kivity Return-path: In-Reply-To: <4FFD4D0A.2000202@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 2012-07-11 11:53, Avi Kivity wrote: > On 07/03/2012 10:21 PM, Alex Williamson wrote: >> Here's the latest iteration of adding an interface to assert and >> de-assert level interrupts from external drivers like vfio. These >> apply on top of the previous argument cleanup, documentation, and >> sanitization patches for irqfd. It would be great to get this queued >> in next for linux 3.6. >> >> I believe I've addressed all the previous comments, including fixing >> the locking problems in eoifd. I've run this with lockdep adding >> and removing level irqfd/eoifd pairs without any problems. Please >> let me know if there are any further comments. Thanks, > > Is there any performance justification for level irqfd? Don't all > new/high bandwidth devices support msi, and this is just a legacy path? I think we've been there before, but the situation hasn't improved much: Apparently, some GPUs still prefer INTx over MSI. Some wireless chipsets too. And then there is not easily replaceable legacy hardware like old telephony adapters or industrial I/O cards etc. that want this. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux