From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755597Ab0IPWNO (ORCPT ); Thu, 16 Sep 2010 18:13:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30554 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754641Ab0IPWNN (ORCPT ); Thu, 16 Sep 2010 18:13:13 -0400 Date: Fri, 17 Sep 2010 00:07:15 +0200 From: "Michael S. Tsirkin" To: Gleb Natapov Cc: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context Message-ID: <20100916220715.GA30531@redhat.com> References: <20100916121338.GA23779@redhat.com> <20100916123301.GE3008@redhat.com> <20100916125717.GA24284@redhat.com> <20100916131823.GH3008@redhat.com> <20100916135137.GB24850@redhat.com> <20100916140615.GJ3008@redhat.com> <20100916142335.GC24850@redhat.com> <20100916145117.GK3008@redhat.com> <20100916152411.GE24850@redhat.com> <20100916154326.GL3008@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100916154326.GL3008@redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 16, 2010 at 05:43:26PM +0200, Gleb Natapov wrote: > On Thu, Sep 16, 2010 at 05:24:11PM +0200, Michael S. Tsirkin wrote: > > On Thu, Sep 16, 2010 at 04:51:17PM +0200, Gleb Natapov wrote: > > > > > What for? Device emulation should do de-assert. > > > > > > > > Sorry, but at this point I have no idea what you call device emulation. > > > The same thing everyone calls device emulation. In case of virtio-net it > > > is in hw/virtio-net.c. If vhost-net is in use device emulation is split > > > between userspace and kernel, but it is still just device emulation. > > > > > > case in point, virtio net does not know about pci at all, > > so it can not deassert. > > > I don't see what PCI has to do with it. virtio-net device implementation is > split between several files. virtio-net/virtio-ring/virtio-pci. All of > them still implement one emulated device. Whoever implemented virtio-net > initially decided to put irq ack register into PCI config space, so code > that does de-assert is in virtio-pci, > but it is still part of emulated > device. > > > > > qemu has code to de-assert. vhost has code to assert. > > > Good. So qemu will de-assert. So what do you mean by > > > "KVM would need to find all irqfd objects mapped to gsi and notify > > > them on deassert" > > > > > > > I would like to optimize level interrupts and stop driving > > > > scheduler insane if at all possible. > > > > > > > Worthy goal. Do it in irqfd. Irqfd shouldn't call kvm_set_irq() if irq > > > level hasn't changed. > > > > Right. Then it needs to know about deasserts. It does not get this > Dessert should be done by qemu writing 0 into irqfd. writing 0 to eventfd does nothing. The way to deassert irq is currently through ioctl and it seems entirely sensible to me to keep it that way. Also - which irqfd :) We need multiple irqfds to map to a single gsi, with kvm doing OR on them. > Assertion and > de-assertion should be done through irqfd. > > information, so when kvm gets deassert ioctl it should > > locate irqfd object and set level to 0. > > See? > No. > > -- > Gleb.