From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04B6FC3A59E for ; Wed, 21 Aug 2019 09:31:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1441A22D6D for ; Wed, 21 Aug 2019 09:31:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727336AbfHUJb2 (ORCPT ); Wed, 21 Aug 2019 05:31:28 -0400 Received: from mga12.intel.com ([192.55.52.136]:11739 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725283AbfHUJb1 (ORCPT ); Wed, 21 Aug 2019 05:31:27 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Aug 2019 02:31:25 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,412,1559545200"; d="scan'208";a="195961705" Received: from linux.intel.com ([10.54.29.200]) by fmsmga001.fm.intel.com with ESMTP; 21 Aug 2019 02:31:24 -0700 Received: from [10.226.38.83] (rtanwar-mobl.gar.corp.intel.com [10.226.38.83]) by linux.intel.com (Postfix) with ESMTP id 970E85803FA; Wed, 21 Aug 2019 02:31:21 -0700 (PDT) Subject: Re: [PATCH] x86/apic: Update virtual irq base for DT/OF based system as well To: Thomas Gleixner Cc: mingo@redhat.com, bp@alien8.de, hpa@zytor.com, tony.luck@intel.com, x86@kernel.org, andriy.shevchenko@intel.com, alan@linux.intel.com, rppt@linux.ibm.com, linux-kernel@vger.kernel.org, qi-ming.wu@intel.com, cheol.yong.kim@intel.com, rahul.tanwar@intel.com References: <20190821081330.1187-1-rahul.tanwar@linux.intel.com> From: "Tanwar, Rahul" Message-ID: <7b4db9f3-21da-5b5e-e219-0170e812a015@linux.intel.com> Date: Wed, 21 Aug 2019 17:31:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/8/2019 4:34 PM, Thomas Gleixner wrote: > Secondly, this link is irrelevant. ioapic_dynirq_base has nothing to do > with virtual IRQ number 0. It's a boundary for the dynamic allocation of > virtual interrupt numbers so that the core allocator does not pick > interrupts out of the IOAPIC's fixed interrupt number space. > > This can be legitimately 0 when IOAPIC is not enabled at all. > > Can you please explain what kind of problem you were seing and what this > really fixes? The problem is that device tree infrastructure considers 0 IRQ value as invalid/error value whereas for ACPI, 0 is a valid value. Without this change, the problem that we see is that the first driver using of_irq_get_xx() or its variants fails because of 0 IRQ number. With this change, allocated IRQ number is never 0 so it works ok.