Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756382AbaGIOGk (ORCPT ); Wed, 9 Jul 2014 10:06:40 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:39467 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755124AbaGIOGj (ORCPT ); Wed, 9 Jul 2014 10:06:39 -0400 X-IronPort-AV: E=Sophos;i="5.01,631,1400025600"; d="scan'208";a="151243364" Message-ID: <53BD4C44.30805@citrix.com> Date: Wed, 9 Jul 2014 15:05:56 +0100 From: Andrew Cooper User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Icedove/24.6.0 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk , David Vrabel CC: , , , Subject: Re: [Xen-devel] [PATCH v3 1/7] xen-pciback: Document the various parameters and attributes in SysFS References: <1404845909-13563-1-git-send-email-konrad@kernel.org> <1404845909-13563-2-git-send-email-konrad@kernel.org> <53BD32C2.6000306@citrix.com> <20140709135922.GD21837@laptop.dumpdata.com> In-Reply-To: <20140709135922.GD21837@laptop.dumpdata.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.18] X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/07/14 14:59, Konrad Rzeszutek Wilk wrote: > >>> +What: /sys/bus/pci/drivers/pciback/irq_handler_state >>> +Date: Oct 2011 >>> +KernelVersion: 3.1 >>> +Contact: xen-devel@lists.xenproject.org >>> +Description: >>> + An option to toggle Xen PCI back to acknowledge (or stop) >>> + interrupts for the specific device regardless of whether the >>> + device is shared, enabled, or on a level interrupt line. >>> + Writing a string of DDDD:BB:DD.F will toggle the state. >>> + This is Domain:Bus:Device.Function where domain is optional. >> I do not understand under what circumstances this should be used in. > So that dom0 does not disable the IRQ line as it would be getting the IRQs > for the guest as well (because the IRQ line is level and another guest > uses an PCI device that is using the same line). Why is this relevant? Xen (and Xen alone) actually controls this aspect of interrupts. Xen manages passing line level interrupts to any domain which might have a device hanging off a particular line, and has to wait until all domains have EOI'd the line until it can clear the interrupt at the IO-APIC. ~Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/