From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:37151 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751837Ab2DJQFn (ORCPT ); Tue, 10 Apr 2012 12:05:43 -0400 Message-ID: <4F845A4E.90003@gmail.com> Date: Wed, 11 Apr 2012 00:05:34 +0800 From: Jiang Liu MIME-Version: 1.0 To: Yinghai Lu CC: Kenji Kaneshige , Taku Izumi , Bjorn Helgaas , Jiang Liu , Keping Chen , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges References: <1333905129-8776-1-git-send-email-jiang.liu@huawei.com> <1333905129-8776-3-git-send-email-jiang.liu@huawei.com> <4F82CB64.8030808@jp.fujitsu.com> <4F830804.6010007@gmail.com> <4F840C3C.2060302@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: On 04/10/2012 11:47 PM, Yinghai Lu wrote: > On Tue, Apr 10, 2012 at 3:32 AM, Kenji Kaneshige > wrote: >> Additionally, I think there is a remaining issue even if we change >> this check like below. >> >> >> if (!!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF)) >> return 0; >> >> I think this check has an assumption that system has at least one >> MCFG table entry and it has been initialized before >> acpi_pci_root_add() is called. I think this doesn't work on the >> system that doesn't have MCFG and all the pci root bridge have >> _CBA (that is, all host bridges are hot-pluggable and BIOS is >> implemented in the way PCI FW spec defines). As a result, MMCONFIG >> would never be enabled on such systems. Could you double check this? > > You are right. > > We can just remove that checking. > > But wonder if current x86_64 system support that. > All peer root buses can be physically removed ? It's theoretically possible that BIOS doesn't provide MMCFG or _CBA for the legacy (non-removable bus 0) host bridge. > > Thanks > > Yinghai