From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751991AbbAMKJP (ORCPT ); Tue, 13 Jan 2015 05:09:15 -0500 Received: from smtp.citrix.com ([66.165.176.89]:1253 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751078AbbAMKJM (ORCPT ); Tue, 13 Jan 2015 05:09:12 -0500 X-IronPort-AV: E=Sophos;i="5.07,748,1413244800"; d="scan'208";a="215253236" Message-ID: <54B4EEC5.1090107@citrix.com> Date: Tue, 13 Jan 2015 10:09:09 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.2.0 MIME-Version: 1.0 To: Jiang Liu , David Vrabel , Sander Eikelenboom , Konrad Rzeszutek Wilk , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , , Boris Ostrovsky , Grant Likely , Yinghai Lu CC: , Subject: Re: [Xen-devel] [PATCH v2] [Bugfix] x86/apic: Fix xen IRQ allocation failure caused by commit b81975eade8c References: <1767175032.20150110201202@eikelenboom.it> <1421069966-19729-1-git-send-email-jiang.liu@linux.intel.com> <54B3E1AC.6080902@citrix.com> <54B48190.9000906@linux.intel.com> In-Reply-To: <54B48190.9000906@linux.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/01/15 02:23, Jiang Liu wrote: > On 2015/1/12 23:01, David Vrabel wrote: >> On 12/01/15 13:39, Jiang Liu wrote: >>> Commit b81975eade8c ("x86, irq: Clean up irqdomain transition code") >>> breaks xen IRQ allocation because xen_smp_prepare_cpus() doesn't invoke >>> setup_IO_APIC(), so no irqdomains created for IOAPICs and >>> mp_map_pin_to_irq() fails at the very beginning. >>> >>> Enhance xen_smp_prepare_cpus() to call setup_IO_APIC() to initialize >>> irqdomain for IOAPICs. >> >> Having Xen call setup_IO_APIC() to initialize the irq domains then having to >> add special cases to it is just wrong. >> >> The bits of init deferred by mp_register_apic() are also deferred to >> two different places which looks odd. >> >> What about something like the following (untested) patch? > Hi David, > Really appreciate your suggestions about Xen IOAPIC:) > Your patch solves the issue, but it will break a coming patch > set to enable hierarchy irqdomain on x86. For 3.19 I would recommend this patch. Since it's been tested and it's pretty small. Can you spin a version of this with a proper changelog. please? > To enable hierarchy irqdomain on x86, need to build > irqdomains in following order: > 1) create irqdomain for CPU vector domain > 2) create irqdomains for interrupt remapping unit if interrupt > remapping is enabled. > 3) create irqdomains for IOAPIC/MSI/HPET etc. > > Function arch_early_ioapic_init() is called before initializing > interrupt remapping subsystem. So creating IOAPIC irqdomains in > arch_early_ioapic_init() will break hierarchy irqdomain with > interrupt remapping enabled. I will post the x86 hierarchy > irqdomain patch soon. > > So could you please help to advice on: I don't know enough about this area to comment on these authoritatively and I don't have time to look into this in more detail right now, but to the best of my understanding. > 1) Is IOAPIC irqdomain needed for PV? PV dom0 only requires a mechanism to obtain properties of the IOAPIC interrupt lines. The actual physical interrupts are delivered to the hypervisor. It doesn't require any of the irq setup. > 2) Is IOAPIC irqdomain needed for HVM? Yes. > 3) Is IOAPIC irqdomain needed for Dom0? See (1) above. > 4) What's the proper hook point to create IOAPIC irqdomain for Xen > UP systems? Don't know. David