Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935317AbaKNQNd (ORCPT ); Fri, 14 Nov 2014 11:13:33 -0500 Received: from service87.mimecast.com ([91.220.42.44]:47652 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935274AbaKNQNc convert rfc822-to-8bit (ORCPT ); Fri, 14 Nov 2014 11:13:32 -0500 Message-ID: <54662A27.6030201@arm.com> Date: Fri, 14 Nov 2014 16:13:27 +0000 From: Marc Zyngier User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130330 Thunderbird/17.0.5 MIME-Version: 1.0 To: Jiang Liu CC: Thomas Gleixner , Bjorn Helgaas , Ingo Molnar , "grant.likely@linaro.org" , Yijing Wang , Yingjoe Chen , Borislav Petkov , "H. Peter Anvin" , Matthias Brugger , Tony Luck , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [Patch V1 0/6] Refine generic/PCI MSI irqodmian interfaces References: <1415879029-20098-1-git-send-email-jiang.liu@linux.intel.com> <54651BE2.9080008@arm.com> <5465227E.6000309@arm.com> <5466259A.7060505@linux.intel.com> In-Reply-To: <5466259A.7060505@linux.intel.com> X-Enigmail-Version: 1.4.6 X-OriginalArrivalTime: 14 Nov 2014 16:13:28.0598 (UTC) FILETIME=[ED224360:01D00025] X-MC-Unique: 114111416132821601 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/11/14 15:54, Jiang Liu wrote: > On 2014/11/14 5:28, Marc Zyngier wrote: >> On 13/11/14 21:11, Thomas Gleixner wrote: >>> On Thu, 13 Nov 2014, Marc Zyngier wrote: >>>> With the new stacked irq domains, it becomes pretty tempting >>>> to allocate an MSI domain per PCI bus, which would remove >>>> the requirement of either relying on arch-specific code, or >>>> a default PCI MSI domain. >>> >>> Right. That's what I roughly had in mind. And that would solve the >>> multi-iommu issue on x86 nicely as well. We establish the association >>> at the time where the bus gets populated. So the whole lookup magic >>> simply goes away. >> >> Great. I've pushed the whole thing out with this patch, the couple >> of fixes I mentioned earlier, as well as the whole ITS code: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/stacked-its-v2 > Hi Marc, > I have looked at the code, and found some issues. > 1) With my next version, no need to implemeent its_pci_msi_free() > anymore. msi_domain_free_irqs() will reset desc->irq to zero > for all architectures. Great. The less code, the better. > 2) This piece of code in its_msi_prepare() may run into trouble > for PCI device with both MSI and MSIX capability. I will change > msi_prepare() prototype to pass in the "nvec" parameter. And you > may access first_pci_msi_entry()->msi_attrib.is_msix to get > allocation type if needed. > nvec = pci_msix_vec_count(pdev); > if (nvec < 0) > nvec = pci_msi_vec_count(pdev); > if (nvec < 0) > return nvec; Ah, good point. Having nvec will make things simpler indeed. I have the feeling that the ITS driver may not be the only one to require such a thing. > 3) Do we need to increase the default of NUM_MSI_ALLOC_SCRATCHPAD_REGS > to 4? 2 is a little too limited. I'd say that 2 is enough for now. The ITS only uses one (the second one is for debug only). Should the need arise, we can bump it up later. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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/