From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f49.google.com ([209.85.219.49]:44215 "EHLO mail-oa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750785Ab3FZEU4 (ORCPT ); Wed, 26 Jun 2013 00:20:56 -0400 Received: by mail-oa0-f49.google.com with SMTP id n9so14106735oag.8 for ; Tue, 25 Jun 2013 21:20:56 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20130620161538.GH3589@8bytes.org> References: <20130528183527.3318.5365.stgit@bling.home> <20130528184020.3318.7800.stgit@bling.home> <20130620135914.GS2575@8bytes.org> <1371743091.32709.52.camel@ul30vt.home> <20130620161538.GH3589@8bytes.org> From: Bjorn Helgaas Date: Tue, 25 Jun 2013 22:20:35 -0600 Message-ID: Subject: Re: [PATCH v2 1/2] iommu: Quirked PCIe bridge test and search function To: Joerg Roedel Cc: Alex Williamson , "open list:INTEL IOMMU (VT-d)" , David Woodhouse , Stephen Hemminger , "linux-pci@vger.kernel.org" , Don Dutile Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, Jun 20, 2013 at 10:15 AM, Joerg Roedel wrote: > On Thu, Jun 20, 2013 at 09:44:51AM -0600, Alex Williamson wrote: >> On Thu, 2013-06-20 at 15:59 +0200, Joerg Roedel wrote: >> > On Tue, May 28, 2013 at 12:40:20PM -0600, Alex Williamson wrote: >> > > + if (!pci_is_root_bus(pdev->bus)) { >> > > + struct pci_dev *parent = pdev->bus->self; >> > > + >> > > + if (pci_is_pcie(parent) && >> > > + pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE) >> > > + return true; >> > > + } >> > >> > Hmm, that looks a bit dangerous. >> >> How so? The algorithm seems pretty simple and logical. > > It is simple, but it is still a heuristic that may fail at some point, > no? > >> Actually, I believe Bjorn rejected the idea of a fixed list because this >> problem is detectable. He also doesn't want me messing with quirks to >> pci_is_pcie() in PCI because he wants a 1:1 relation between that and >> having a PCIe capability. So, I'm stuck and this is where it's ended >> up. Thanks, > > I think implementing such a list is much safer. > > Bjorn, why didn't you like that idea? Sorry, I can't remember, and I haven't been able to find the discussion where I said that. I think the current patches are all in drivers/iommu, and if a list makes sense there, it's fine with me. Bjorn