From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: vfio with iommu groups Date: Mon, 14 May 2012 14:29:20 +1000 Message-ID: <1336969760.6727.17.camel@pasglop> References: <4FAE11DC.1050401@ozlabs.ru> <1336968971.6954.41.camel@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Alexey Kardashevskiy , qemu-devel@nongnu.org, Alex Graf , anthony@codemonkey.ws, David Gibson To: Alex Williamson Return-path: In-Reply-To: <1336968971.6954.41.camel@bling.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org On Sun, 2012-05-13 at 22:16 -0600, Alex Williamson wrote: > > However theoretically we might want to show these 3 PCIe bridges as well (but not the root complex). > > For example, INTx lines should be swizzled when the guest parses a device tree and > > tries to calculate a real IRQ number. VFIO does not handles bridges at all, it treats them as PCI > > functions. > > > > Is there any idea what to do with bridges? > > I don't really have a problem with the idea of exposing bridges, but it > get's pretty complicated. What happens if the guest reprograms the > subordinate bus numbers? Is there any advantage vs exposing an emulated > bridge in it's place? Do you have a proposal for it? Thanks, I think exposing an emulated bridge would be more in the "spirit" of the current vfio and safer for now (long run, as we already discussed, we might look at an other option with more direct HW access for power). We do want to expose those bridges one way or another for the sake of getting the interrupt routing right, since the guest will make assumptions based on those bridges to calculate the proper swizzling. Cheers, Ben.