Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933679AbcDLVOq (ORCPT ); Tue, 12 Apr 2016 17:14:46 -0400 Received: from mail.kernel.org ([198.145.29.136]:48111 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933250AbcDLVOn (ORCPT ); Tue, 12 Apr 2016 17:14:43 -0400 Date: Tue, 12 Apr 2016 14:14:39 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-X260 To: Boris Ostrovsky cc: Stefano Stabellini , Vitaly Kuznetsov , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jiang Liu , "K. Y. Srinivasan" , linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, david.vrabel@citrix.com, jgross@suse.com Subject: Re: Xen regression, Was: [PATCH] x86/irq: Probe for PIC presence before allocating descs for legacy IRQs In-Reply-To: <570D4645.20004@oracle.com> Message-ID: References: <1446470676-1877-1-git-send-email-vkuznets@redhat.com> <570CF69A.1020701@oracle.com> <570D4645.20004@oracle.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2919 Lines: 79 On Tue, 12 Apr 2016, Boris Ostrovsky wrote: > On 04/12/2016 02:06 PM, Stefano Stabellini wrote: > > On Tue, 12 Apr 2016, Boris Ostrovsky wrote: > > > On 04/11/2016 10:08 PM, Stefano Stabellini wrote: > > > > Hi all, > > > > > > > > Unfortunately this patch (now commit > > > > 8c058b0b9c34d8c8d7912880956543769323e2d8) causes a regression on Xen > > > > when running on top of QEMU: the number of PIT irqs get set to 0 by > > > > probe_8259A but actually there are 16. > > > > > > > > Any suggestions on how to fix this? > > > > > > > > 1) we could revert 8c058b0b9c34d8c8d7912880956543769323e2d8 > > > > 2) we could introduce an 'if (!xen_domain())' in probe_8259A > > > > 3) suggestions welcome > > > Stefano, do you have b4ff8389ed14b849354b59ce9b360bdefcdbf99c ? > > > > > > It was supposed to fix this problem for Xen. However, I just noticed that > > > arch/arm64/include/asm/irq.h makes nr_legacy_irqs() return 0 (unlike > > > arch/arm/include/asm/irq.h). Could that be the problem? > > I have b4ff8389ed14b849354b59ce9b360bdefcdbf99c but it doesn't fix the > > issue for me. > > > > Is the idea of your patch that xen_allocate_irq_gsi will allocate the > > descriptor dynamically instead? > > Right. > > > If so, it doesn't work because it > > doesn't get called for irq 14: > > So how has it worked until now then? It didn't for me :-) Maybe it was working for DomUs, but not for Dom0? > > piix_init_one -> ata_pci_sff_activate_host -> devm_request_irq -> > > devm_request_threaded_irq-> request_threaded_irq -> irq_to_desc(14) -> > > -EVAIL > > > > If you look at pci_xen_initial_domain, the loop: > > > > for (irq = 0; irq < nr_legacy_irqs(); irq++) { > > > > won't work anymore because by the time is called, nr_legacy_irqs() > > already returns 0, because it has been changed by probe_8259A(). > > > > We also need the following patch: > > > > --- > > > > xen/x86: actually allocate legacy interrupts on PV guests > > > > b4ff8389ed14 is incomplete: relies on nr_legacy_irqs() to get the number > > of legacy interrupts when actually nr_legacy_irqs() returns 0 after > > probe_8259A(). Use NR_IRQS_LEGACY instead. > > > > Signed-off-by: Stefano Stabellini > > > > diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c > > index beac4df..6db0060 100644 > > --- a/arch/x86/pci/xen.c > > +++ b/arch/x86/pci/xen.c > > @@ -492,7 +492,7 @@ int __init pci_xen_initial_domain(void) > > __acpi_register_gsi = acpi_register_gsi_xen; > > __acpi_unregister_gsi = NULL; > > /* Pre-allocate legacy irqs */ > > - for (irq = 0; irq < nr_legacy_irqs(); irq++) { > > + for (irq = 0; irq < NR_IRQS_LEGACY; irq++) { > > int trigger, polarity; > > if (acpi_get_override_irq(irq, &trigger, &polarity) == -1) > > > Won't we need the same change in the 'if (0 == nr_ioapics)' clause? That's not a problem: there is 1 ioapic in my system and is detected correctly.