From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Burns Subject: Re: MMIO ioremap() error with PCI passthrough Date: Tue, 01 Jul 2008 23:27:30 +0100 Message-ID: <486AAF52.2050701@adslpipe.co.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 01/07/2008 20:57, Keir Fraser wrote: > Interrupt sharing generally depends on which lines are > wired together on your mainboard. When Xen receives an interrupt on a shared > line it does not have enough information to demultiplex that interrupt to > the appropriate receiver -- it has to broadcast to all potential recipients. OK. Sucking data at several Mb/s from a tv tuner, then squirting it to disk, where the tuner and disk are sharing the same interrupt doesn't sound ideal then ;-) The SATA controller is presently performing an online mdraid reshape from 6 to 8 disks, averaging 6000 interrupts per second, so that's probably what is triggering the 99,900 "ignored" interrupts in 40 seconds! > I have no idea what IOAPIC[1] above really represents. Usually the GSI range > for an IOAPIC corresponds to its array of interrupt input pins. I've never > heard of a 256-pin IOAPIC! Could it relate to MSI? > The best you could hope for would be to try out the MSI/MSI-X support in the > xen-unstable tree (soon to be Xen 3.3). These are message-based interrupts > which completely sidesteps the issue of interrupt lines and their wiring > together. Sounds good, but I gather it's only for PCIe or PCI2.3 devices, so my present tuners won't directly benefit, I suppose they might benefit indirectly by other devices using MSI and freeing up hardwired interrupts rather than being shared. Longer term I'll probably get a PCIe dual tuner. Thanks for you help today, it'll likely be the weekend before I can look into this any further.