From: "Michael S. Tsirkin" Subject: Re: [PATCH 1/2] kvm: fix spurious interrupt with irqfd Date: Tue, 19 Jan 2010 16:29:02 +0200 Message-ID: <20100119142902.GA28465@redhat.com> References: <20100113171230.GB19798@redhat.com> <4B55B2B8.5090105@siemens.com> <20100119134827.GA28191@redhat.com> <4B55BBB6.2020901@siemens.com> <20100119140425.GA28410@redhat.com> <4B55C05D.9000509@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Davide Libenzi , Avi Kivity , "kvm@vger.kernel.org" , Linux Kernel Mailing List To: Jan Kiszka Return-path: Content-Disposition: inline In-Reply-To: <4B55C05D.9000509@siemens.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Jan 19, 2010 at 03:23:25PM +0100, Jan Kiszka wrote: > Michael S. Tsirkin wrote: > >>>> I just wonder how broad > >>>> the impact of a broken or non-existent eventfd subsystem for kvm-kmod > >>>> is. Any thoughts welcome. > >>> How do you handle kernels that don't export eventfd_ctx_fileget? > >> Now that you mention it: not yet properly. So far we pass the file > >> struct as pseudo eventfd_ctx around on < 2.6.31. But now that I peek > >> into the struct in kvm_eventfd_ctx_remove_wait_queue, this should should > >> crash. Guess I need to look up that module the same way as I acquire > >> __wake_up_locked[_key]. > > > > This won't work that well: eventfd in upstream > > sends us POLLHUP so we can close the structure, > > in old kernels it doesn't so kernel will crash > > when we try to reference the structure later. > > > > OK, so any host kernel < 2.6.31 will never work for us. Mmh, then I > could only close the gap 2.6.31..2.6.33. vhost will show up in 33... > Will that version already be worth any eventfd wrapping? > > Jan I asked Avi to send a patch upstream into 2.6.32.X fixing spurious interrupts there. 2.6.31-stable is closed unfortunately, so we won't be able to support it. Disable eventfd there? > -- > Siemens AG, Corporate Technology, CT T DE IT 1 > Corporate Competence Center Embedded Linux