From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:50099 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751806AbbEKOcU (ORCPT ); Mon, 11 May 2015 10:32:20 -0400 Date: Mon, 11 May 2015 10:32:11 -0400 From: Konrad Rzeszutek Wilk To: Mark Hounschell Cc: wdavis@nvidia.com, linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org, jglisse@redhat.com, jhubbard@nvidia.com, tripperda@nvidia.com Subject: Re: [PATCH 0/6] IOMMU/DMA map_resource support for peer-to-peer Message-ID: <20150511143211.GE20282@l.oracle.com> References: <1430505138-2877-1-git-send-email-wdavis@nvidia.com> <20150508202134.GB26795@l.oracle.com> <554D2099.2030907@compro.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <554D2099.2030907@compro.net> Sender: linux-pci-owner@vger.kernel.org List-ID: On Fri, May 08, 2015 at 04:46:17PM -0400, Mark Hounschell wrote: > On 05/08/2015 04:21 PM, Konrad Rzeszutek Wilk wrote: > >On Fri, May 01, 2015 at 01:32:12PM -0500, wdavis@nvidia.com wrote: > >>From: Will Davis > >> > >>Hi, > >> > >>This patch series adds DMA APIs to map and unmap a struct resource to and from > >>a PCI device's IOVA domain, and implements the AMD, Intel, and nommu versions > >>of these interfaces. > >> > >>This solves a long-standing problem with the existing DMA-remapping interfaces, > >>which require that a struct page be given for the region to be mapped into a > >>device's IOVA domain. This requirement cannot support peer device BAR ranges, > >>for which no struct pages exist. > >> > >>The underlying implementations of map_page and map_sg convert the struct page > >>into its physical address anyway, so we just need a way to route the physical > >>address of the BAR region to these implementations. The new interfaces do this > >>by taking the struct resource describing a device's BAR region, from which the > >>physical address is derived. > >> > >>The Intel and nommu versions have been verified on a dual Intel Xeon E5405 > >>workstation. I'm in the process of obtaining hardware to test the AMD version > >>as well. Please review. > > > >Does it work if you boot with 'iommu=soft swiotlb=force' which will mandate > >an strict usage of the DMA API? > > > > PCIe peer2peer is borked on all motherboards I've tried. Only writes are :-( > possible. Reads are not supported. I suppose if you have a platform with > only PCI and an IOMMU this would be very useful. Without both read and write > PCIe peer2peer support, this seems unnecessary. > It is a perfect way to test the code to make sure the API works (or it fails in the failure modes) _and_ that the drivers as well (use the pci_map_sync, and so on). > Mark > >