From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753892AbcEWJYF (ORCPT ); Mon, 23 May 2016 05:24:05 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:35984 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753873AbcEWJYB (ORCPT ); Mon, 23 May 2016 05:24:01 -0400 Date: Mon, 23 May 2016 17:23:53 +0800 From: Peng Fan To: Eric Auger Cc: alex.williamson@redhat.com, b.reynal@virtualopensystems.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] vfio: platform: support No-IOMMU mode Message-ID: <20160523092352.GB5377@linux-7smt.suse> References: <1463991250-980-1-git-send-email-van.freenix@gmail.com> <5742C66C.90203@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5742C66C.90203@linaro.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Eric, On Mon, May 23, 2016 at 10:59:24AM +0200, Eric Auger wrote: >Hi Peng, >On 05/23/2016 10:14 AM, Peng Fan wrote: >> The vfio No-IOMMU mode was supported by this >> 'commit 03a76b60f8ba2797 ("vfio: Include No-IOMMU mode")', >> but it only support vfio-pci. >> >> Using vfio_iommu_group_get/put, but not iommu_group_get/put, >> the platform devices can be exposed to userspace with >> CONFIG_VFIO_NOIOMMU and the "enable_unsafe_noiommu_mode" >> option enabled. >> >> From 'commit 03a76b60f8ba2797 ("vfio: Include No-IOMMU mode")', >> "This should make it very clear that this mode is not safe. >> Additionally, CAP_SYS_RAWIO privileges are necessary to work >> with groups and containers using this mode. Groups making >> use of this support are named /dev/vfio/noiommu-$GROUP and >> can only make use of the special VFIO_NOIOMMU_IOMMU for the >> container. Use of this mode, specifically binding a device >> without a native IOMMU group to a VFIO bus driver will taint >> the kernel and should therefore not be considered supported.", >> >> Actually, for vfio-platform No-IOMMU mode, the userspace can >> not do DMA, because the ioctl API of noiommu container only >> supports VFIO_CHECK_EXTENSION and VFIO_IOMMU_MAP_DMA is not >> supported. >I did not play with no-iommu mode yet but I am surprised by this last >sentence. Without IOMMU the VFIO_IOMMU_MAP_DMA ioctl is not relevant >since you do not need to and cannot map anything but does this really >mean the device cannot perform DMA transfers towards physical memory, if >programmed to do so; I don't think so? Sorry. My commit log maybe misleading, I mean we can not use mmap + VFIO_IOMMU_MAP_DMA for noiommu. The platform device can still do DMA, if we program the DMA address for the device correctly, such as a reserved memory region. I can discard the last sentence of the commit log in V3. Thanks, Peng. > >Best Regards > >Eric >> >> Signed-off-by: Peng Fan >> Cc: Eric Auger >> Cc: Baptiste Reynal >> Cc: Alex Williamson >> --- >> >> V2: >> Rename subject to support No-IOMMU >> Add more commit log. >> >> I wrote a simple program following this >> https://github.com/virtualopensystems/vfio-host-test/blob/master/src_test/vfio_device_test.c >> ,no dma support. The device's register can be >> accessed in userspace using command './vfio_dev_test 30b60000.usdhc 0 1 platform' >> >> drivers/vfio/platform/vfio_platform_common.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c >> index e65b142..993b2f9 100644 >> --- a/drivers/vfio/platform/vfio_platform_common.c >> +++ b/drivers/vfio/platform/vfio_platform_common.c >> @@ -561,7 +561,7 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev, >> >> vdev->device = dev; >> >> - group = iommu_group_get(dev); >> + group = vfio_iommu_group_get(dev); >> if (!group) { >> pr_err("VFIO: No IOMMU group for device %s\n", vdev->name); >> return -EINVAL; >> @@ -569,7 +569,7 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev, >> >> ret = vfio_add_group_dev(dev, &vfio_platform_ops, vdev); >> if (ret) { >> - iommu_group_put(group); >> + vfio_iommu_group_put(group, dev); >> return ret; >> } >> >> @@ -589,7 +589,7 @@ struct vfio_platform_device *vfio_platform_remove_common(struct device *dev) >> >> if (vdev) { >> vfio_platform_put_reset(vdev); >> - iommu_group_put(dev->iommu_group); >> + vfio_iommu_group_put(dev->iommu_group, dev); >> } >> >> return vdev; >> >