From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755824AbaCNQu2 (ORCPT ); Fri, 14 Mar 2014 12:50:28 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:33431 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755445AbaCNQu0 (ORCPT ); Fri, 14 Mar 2014 12:50:26 -0400 Message-ID: <5323334F.90700@linaro.org> Date: Fri, 14 Mar 2014 16:50:23 +0000 From: Julien Grall User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20131104 Icedove/17.0.10 MIME-Version: 1.0 To: Stefano Stabellini , "gregkh@linuxfoundation.org" , Russell King CC: Ian Campbell , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, xen-devel@lists.xenproject.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Rob Landley , devicetree@vger.kernel.org Subject: Re: [PATCH 2/2] arm/xen: Don't use xen DMA ops when the device is protected by an IOMMU References: <1392913301-25524-1-git-send-email-julien.grall@linaro.org> <1392914159.32657.18.camel@kazak.uk.xensource.com> <20140224151636.GA13489@kroah.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/24/2014 08:49 PM, Stefano Stabellini wrote: > On Mon, 24 Feb 2014, gregkh@linuxfoundation.org wrote: > Julien is proposing to store the list of "safe" devices on an hash table > in the Xen specific code (in arch/arm/xen/enlighten.c, see > http://marc.info/?l=linux-kernel&m=139291370526082&w=2). > Whenever Linux is about to do DMA, we would check in the hashtable to > figure out whether we need to go through the swiotlb or we can simply > use the native dma_ops. > > Ian and I were thinking that it would be much easier and faster to have > a "xen_safe_device" parameter in struct device and just check for that. > It doesn't actually need to be in struct device, it could simply be a > flag in struct device_dma_parameters as Ian was suggesting. > > Julien, could you please come up with a simple patch to demonstrate the > concept? Hello Stefano and Greg, Sorry for the late answer. I wrote a simple patch which depend on patch #1. Let me know if it's the right direction. Regards, commit ca55e82bc191678b284792d2f0d200fa1ce08e16 Author: Julien Grall Date: Fri Mar 14 16:27:01 2014 +0000 ARM: platform_device: dev_archdata: Add xen specific boolean Until now, every DMA-capable devices are using specific Xen DMA ops when Linux is running as DOM0. These DMA ops call swiotlb-xen to bounce buffer. With the support of IOMMU drivers in Xen, every device protected by IOMMU must not use swiotlb DMA ops. This patch introduces a boolean in dev_archdata to indicate if the device can safely use its own DMA ops or swiotlb ops. Signed-off-by: Julien Grall diff --git a/arch/arm/include/asm/device.h b/arch/arm/include/asm/device.h index dc662fc..345a96e 100644 --- a/arch/arm/include/asm/device.h +++ b/arch/arm/include/asm/device.h @@ -17,6 +17,9 @@ struct dev_archdata { #ifdef CONFIG_ARM_DMA_USE_IOMMU struct dma_iommu_mapping *mapping; #endif +#ifdef CONFIG_XEN + bool is_protected; +#endif }; struct omap_device; diff --git a/arch/arm/include/asm/xen/dma-mapping.h b/arch/arm/include/asm/xen/dma-mapping.h index 002fc57..d6cc012 100644 --- a/arch/arm/include/asm/xen/dma-mapping.h +++ b/arch/arm/include/asm/xen/dma-mapping.h @@ -5,9 +5,21 @@ extern struct dma_map_ops *xen_dma_ops; +#ifdef CONFIG_XEN +static inline bool xen_is_protected_device(const struct device *dev) +{ + return dev->archdata.is_protected; +} +#else +static inline bool xen_is_protected_device(const struct device *dev) +{ + return 0; +} +#endif + static inline bool need_xen_dma_ops(struct device *dev) { - return xen_initial_domain(); + return xen_initial_domain() && !xen_is_protected_device(dev); } #endif /* _ASM_ARM_XEN_DMA_MAPPING_H */ -- Julien Grall