From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nat28.tlf.novell.com ([130.57.49.28]:47223 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752907Ab3DZHPq convert rfc822-to-8bit (ORCPT ); Fri, 26 Apr 2013 03:15:46 -0400 Message-Id: <517A45E602000078000D0F78@nat28.tlf.novell.com> Date: Fri, 26 Apr 2013 08:16:22 +0100 From: "Jan Beulich" To: "Bjorn Helgaas" Cc: "Jeremy Fitzhardinge" , "Gavin Shan" , , "Konrad Rzeszutek Wilk" , "linux-pci@vger.kernel.org" Subject: Re: [Xen-devel] [PATCH v4 18/22] xen/pci: Pay attention to PCI_MSIX_TABLE_OFFSET References: <20130422230012.32621.15224.stgit@bhelgaas-glaptop> <20130422231214.32621.37394.stgit@bhelgaas-glaptop> <5179164902000078000D0A26@nat28.tlf.novell.com> <20130425164238.GA3052@google.com> In-Reply-To: <20130425164238.GA3052@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-pci-owner@vger.kernel.org List-ID: >>> On 25.04.13 at 18:42, Bjorn Helgaas wrote: > On Thu, Apr 25, 2013 at 10:40:57AM +0100, Jan Beulich wrote: >> Recent hypervisors will actually >> only consume this to issue a warning if not matching what gets >> read from the corresponding BAR. Earlier hypervisors used this >> instead of reading the BAR. > > Note that pci_resource_start() gives you a CPU address, and what you > read from the BAR is a PCI bus address. These are not in the same > address space and can't be directly compared. I assume the > hypervisors take that into account and do the appropriate > conversions? I suppose Xen has never been run on a system where the two would differ, and it's quite likely that it would break on such systems. Question is - are there any x86-based systems where this is the case? Jan From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [Xen-devel] [PATCH v4 18/22] xen/pci: Pay attention to PCI_MSIX_TABLE_OFFSET Date: Fri, 26 Apr 2013 08:16:22 +0100 Message-ID: <517A45E602000078000D0F78@nat28.tlf.novell.com> References: <20130422230012.32621.15224.stgit@bhelgaas-glaptop> <20130422231214.32621.37394.stgit@bhelgaas-glaptop> <5179164902000078000D0A26@nat28.tlf.novell.com> <20130425164238.GA3052@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20130425164238.GA3052@google.com> Content-Disposition: inline Sender: linux-pci-owner@vger.kernel.org To: Bjorn Helgaas Cc: Jeremy Fitzhardinge , Gavin Shan , xen-devel@lists.xensource.com, Konrad Rzeszutek Wilk , "linux-pci@vger.kernel.org" List-Id: xen-devel@lists.xenproject.org >>> On 25.04.13 at 18:42, Bjorn Helgaas wrote: > On Thu, Apr 25, 2013 at 10:40:57AM +0100, Jan Beulich wrote: >> Recent hypervisors will actually >> only consume this to issue a warning if not matching what gets >> read from the corresponding BAR. Earlier hypervisors used this >> instead of reading the BAR. > > Note that pci_resource_start() gives you a CPU address, and what you > read from the BAR is a PCI bus address. These are not in the same > address space and can't be directly compared. I assume the > hypervisors take that into account and do the appropriate > conversions? I suppose Xen has never been run on a system where the two would differ, and it's quite likely that it would break on such systems. Question is - are there any x86-based systems where this is the case? Jan