From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:41659) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1STmub-0005xS-Gc for qemu-devel@nongnu.org; Mon, 14 May 2012 00:29:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1STmuZ-0003mj-SD for qemu-devel@nongnu.org; Mon, 14 May 2012 00:29:33 -0400 Received: from gate.crashing.org ([63.228.1.57]:43004) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1STmuZ-0003ka-Ib for qemu-devel@nongnu.org; Mon, 14 May 2012 00:29:31 -0400 Message-ID: <1336969760.6727.17.camel@pasglop> From: Benjamin Herrenschmidt Date: Mon, 14 May 2012 14:29:20 +1000 In-Reply-To: <1336968971.6954.41.camel@bling.home> References: <4FAE11DC.1050401@ozlabs.ru> <1336968971.6954.41.camel@bling.home> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Subject: Re: [Qemu-devel] vfio with iommu groups List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: kvm@vger.kernel.org, Alexey Kardashevskiy , qemu-devel@nongnu.org, Alex Graf , anthony@codemonkey.ws, David Gibson 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.