From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751915AbcFVH3K (ORCPT ); Wed, 22 Jun 2016 03:29:10 -0400 Received: from mga02.intel.com ([134.134.136.20]:26323 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750896AbcFVH3H (ORCPT ); Wed, 22 Jun 2016 03:29:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,509,1459839600"; d="scan'208";a="832982935" From: Rui Wang To: helgaas@kernel.org Cc: tglx@linutronix.de, rjw@rjwysocki.net, tony.luck@intel.com, bhelgaas@google.com, linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, rui.y.wang@intel.com Subject: RE: [PATCH V3 1/3] x86/ioapic: Support hot-removal of IOAPICs present during boot Date: Wed, 22 Jun 2016 15:13:32 +0800 Message-Id: <1466579612-20417-1-git-send-email-rui.y.wang@intel.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <20160616170958.GA7250@localhost> References: <20160616170958.GA7250@localhost> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, June 17, 2016 1:10 AM, Bjorn Helgaas wrote: > ioapic_insert_resources() is x86-specific, but I'm not sure why; it seems > like it does things that should be applicable to ia64 as well. > > acpi_ioapic_add() is not x86-specific, and it is called from > acpi_pci_root_add() for the hot-add case. You're adding an x86-xpecific call > in pci_assign_unassigned_resources(). Why should the hot-add case be for > all arches, but the boot-time case only for x86? Hi Bjorn, It turns out that IOAPIC hotplug has not been pursued on ia64. There were demos showing CPU sockets online/offline on ia64 but the CPUs had no IIO, thus no IOAPIC hotplug. So to answer the first question: ioapic_insert_resources() is x86-specific because it's inserting what has been setup in io_apic_init_mappings() which, through mpc_ioapic_addr(), is capable of handling both the static case (acpi_parse_ioapic(), etc.) and the hotplug case (acpi_ioapic_add()). But on ia64, there's only the static case through acpi_parse_iosapic(), no need for the hotplug case yet. To answer the second question: acpi_ioapic_add() is in effect x86-specific, because it's an empty function when CONFIG_ACPI_HOTPLUG_IOAPIC isn't defined. And CONFIG_ACPI_HOTPLUG_IOAPIC depends on CONFIG_X86_IO_APIC (see drivers/acpi/Kconfig). This was introduced in c183619b6 (x86/irq, ACPI: Implement ACPI driver to support IOAPIC hotplug). That commit shows the dependency. I'll send a newer version with comments explaining these. Thanks Rui