From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [PATCH v10 2/2] kvm: Add resampling irqfds for level triggered interrupts Date: Wed, 19 Sep 2012 07:54:32 -0600 Message-ID: <1348062872.28860.24.camel@bling.home> References: <20120918031156.12021.27838.stgit@bling.home> <20120918031626.12021.90083.stgit@bling.home> <50598975.50503@redhat.com> <20120919090845.GA26517@redhat.com> <50598C1D.4050206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: In-Reply-To: <50598C1D.4050206@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, 2012-09-19 at 12:10 +0300, Avi Kivity wrote: > On 09/19/2012 12:08 PM, Michael S. Tsirkin wrote: > > >> Whoa. Can't we put the resampler entry somewhere we don't need to > >> search for it? Like a kvm_kernel_irq_routing_entry, that's indexed by > >> gsi already (kvm_irq_routing_table::rt_entries[gsi]). > > > > I'm not sure why would we bother optimizing this, > > Not optimizing, simplifying. > > > but if we do, I guess we could look for the irq notifier > > which is already indexed by gsi. > > It's not, it's looked up in a list. I'm not sure it's a simplification because to index by gsi we suddenly need to care how many gsis there are. I believe that currently means we have to assume an ioapic. Creating a dumb list is a little bit of overhead, but we get to stay blissfully unaware of the gsi implementation. Practically we're looking at a list of 4 entries, maybe a few times that when we expose more PCI root bridges to the guest. Thanks, Alex