Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965780AbcDLSGn (ORCPT ); Tue, 12 Apr 2016 14:06:43 -0400 Received: from mail.kernel.org ([198.145.29.136]:35509 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965083AbcDLSGl (ORCPT ); Tue, 12 Apr 2016 14:06:41 -0400 Date: Tue, 12 Apr 2016 11:06:37 -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: <570CF69A.1020701@oracle.com> Message-ID: References: <1446470676-1877-1-git-send-email-vkuznets@redhat.com> <570CF69A.1020701@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: 2292 Lines: 64 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? If so, it doesn't work because it doesn't get called for irq 14: 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)