From: "Michael S. Tsirkin" Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context Date: Sun, 19 Sep 2010 13:21:24 +0200 Message-ID: <20100919112124.GD7350@redhat.com> References: <20100916142335.GC24850@redhat.com> <20100916145117.GK3008@redhat.com> <20100916152411.GE24850@redhat.com> <20100916154326.GL3008@redhat.com> <20100916220715.GA30531@redhat.com> <20100917075929.GA11518@redhat.com> <20100919104550.GA7350@redhat.com> <4C95EC4C.4060904@redhat.com> <20100919105512.GB7350@redhat.com> <20100919111844.GQ3008@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Gleb Natapov Return-path: Content-Disposition: inline In-Reply-To: <20100919111844.GQ3008@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Sun, Sep 19, 2010 at 01:18:44PM +0200, Gleb Natapov wrote: > On Sun, Sep 19, 2010 at 12:55:12PM +0200, Michael S. Tsirkin wrote: > > On Sun, Sep 19, 2010 at 12:56:12PM +0200, Avi Kivity wrote: > > > On 09/19/2010 12:45 PM, Michael S. Tsirkin wrote: > > > >On Fri, Sep 17, 2010 at 09:59:29AM +0200, Gleb Natapov wrote: > > > >> > writing 0 to eventfd does nothing. The way to deassert irq > > > >> That is implementation detail of current irqfd. It was designed for MSI > > > >> not level triggered interrupts. > > > > > > > >Maybe we should add a check that gsi is mapped to MSI (or unmapped) then? > > > >Level which switches to 1 and back to 0 immediately will be racy anyway > > > >... > > > > > > > > > > Add a check where? > > > > I would make sure that if you bind irqfd to a non-MSI GSI, > > signalling it has no effect. > > > Why would you do that? I am not against checking per se, but why a user of > the API can't check for that? > > -- > Gleb. Currently using irqfd with level will kind of work, sometimes. Better have it consistently not working so application writers get the message that they can't rely on it. -- MST