From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20EBDC35DF5 for ; Tue, 25 Feb 2020 03:53:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E959E24650 for ; Tue, 25 Feb 2020 03:53:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728921AbgBYDxz (ORCPT ); Mon, 24 Feb 2020 22:53:55 -0500 Received: from mga02.intel.com ([134.134.136.20]:13814 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726962AbgBYDxy (ORCPT ); Mon, 24 Feb 2020 22:53:54 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Feb 2020 19:53:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,482,1574150400"; d="scan'208";a="316951958" Received: from joy-optiplex-7040.sh.intel.com (HELO joy-OptiPlex-7040) ([10.239.13.16]) by orsmga001.jf.intel.com with ESMTP; 24 Feb 2020 19:53:51 -0800 Date: Mon, 24 Feb 2020 22:44:28 -0500 From: Yan Zhao To: Alex Williamson Cc: "zhenyuw@linux.intel.com" , "intel-gvt-dev@lists.freedesktop.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "pbonzini@redhat.com" , "Tian, Kevin" , "peterx@redhat.com" Subject: Re: [PATCH v3 2/7] vfio: introduce vfio_dma_rw to read/write a range of IOVAs Message-ID: <20200225034428.GF30338@joy-OptiPlex-7040> Reply-To: Yan Zhao References: <20200224084350.31574-1-yan.y.zhao@intel.com> <20200224084715.31753-1-yan.y.zhao@intel.com> <20200224121442.297a9931@w520.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200224121442.297a9931@w520.home> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 25, 2020 at 03:14:42AM +0800, Alex Williamson wrote: > On Mon, 24 Feb 2020 03:47:15 -0500 > Yan Zhao wrote: > > > vfio_dma_rw will read/write a range of user space memory pointed to by > > IOVA into/from a kernel buffer without enforcing pinning the user space > > memory. > > > > TODO: mark the IOVAs to user space memory dirty if they are written in > > vfio_dma_rw(). > > > > Cc: Kevin Tian > > Signed-off-by: Yan Zhao > > --- > > drivers/vfio/vfio.c | 49 +++++++++++++++++++++ > > drivers/vfio/vfio_iommu_type1.c | 77 +++++++++++++++++++++++++++++++++ > > include/linux/vfio.h | 5 +++ > > 3 files changed, 131 insertions(+) > > > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > > index 914bdf4b9d73..902867627cbf 100644 > > --- a/drivers/vfio/vfio.c > > +++ b/drivers/vfio/vfio.c > > @@ -1998,6 +1998,55 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage) > > } > > EXPORT_SYMBOL(vfio_unpin_pages); > > > > + > > +/* > > + * This interface allows the CPUs to perform some sort of virtual DMA on > > + * behalf of the device. > > + * > > + * CPUs read/write a range of IOVAs pointing to user space memory into/from > > + * a kernel buffer. > > + * > > + * As the read/write of user space memory is conducted via the CPUs and is > > + * not a real device DMA, it is not necessary to pin the user space memory. > > + * > > + * The caller needs to call vfio_group_get_external_user() or > > + * vfio_group_get_external_user_from_dev() prior to calling this interface, > > + * so as to prevent the VFIO group from disposal in the middle of the call. > > + * But it can keep the reference to the VFIO group for several calls into > > + * this interface. > > + * After finishing using of the VFIO group, the caller needs to release the > > + * VFIO group by calling vfio_group_put_external_user(). > > + * > > + * @group [in]: vfio group of a device > > + * @iova [in] : base IOVA of a user space buffer > > + * @data [in] : pointer to kernel buffer > > + * @len [in] : kernel buffer length > > + * @write : indicate read or write > > + * Return error code on failure or 0 on success. > > + */ > > +int vfio_dma_rw(struct vfio_group *group, dma_addr_t iova, > > + void *data, size_t len, bool write) > > +{ > > + struct vfio_container *container; > > + struct vfio_iommu_driver *driver; > > + int ret = 0; > > + > > + if (!group || !data || len <= 0) > > + return -EINVAL; > > + > > + container = group->container; > > + driver = container->iommu_driver; > > + > > + if (likely(driver && driver->ops->dma_rw)) > > + ret = driver->ops->dma_rw(container->iommu_data, > > + iova, data, len, write); > > + else > > + ret = -ENOTTY; > > + > > + return ret; > > +} > > +EXPORT_SYMBOL(vfio_dma_rw); > > + > > static int vfio_register_iommu_notifier(struct vfio_group *group, > > unsigned long *events, > > struct notifier_block *nb) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > > index 2ada8e6cdb88..74e1c425943c 100644 > > --- a/drivers/vfio/vfio_iommu_type1.c > > +++ b/drivers/vfio/vfio_iommu_type1.c > > @@ -27,6 +27,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -2326,6 +2327,81 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data, > > return blocking_notifier_chain_unregister(&iommu->notifier, nb); > > } > > > > +static size_t vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu, > > + dma_addr_t iova, void *data, > > + size_t count, bool write) > > +{ > > + struct mm_struct *mm; > > + unsigned long vaddr; > > + struct vfio_dma *dma; > > + bool kthread = current->mm == NULL; > > + size_t done = 0; > > + size_t offset; > > + > > + dma = vfio_find_dma(iommu, iova, 1); > > + if (!dma) > > + return 0; > > + > > + if ((write && !(dma->prot & IOMMU_WRITE)) || > > + !(dma->prot & IOMMU_READ)) > > + return 0; > > + > > + mm = get_task_mm(dma->task); > > + > > + if (!mm) > > + return 0; > > + > > + if (kthread) > > + use_mm(mm); > > + else if (current->mm != mm) > > + goto out; > > + > > + offset = iova - dma->iova; > > + > > + if (count > dma->size - offset) > > + count = dma->size - offset; > > + > > + vaddr = dma->vaddr + offset; > > + > > + if (write) > > + done = __copy_to_user((void __user *)vaddr, > > + data, count) ? 0 : count; > > + else > > + done = __copy_from_user(data, (void __user *)vaddr, > > + count) ? 0 : count; > > + > > + if (kthread) > > + unuse_mm(mm); > > +out: > > + mmput(mm); > > + return done; > > > Return 0 on error? Why wouldn't this function decide the errno rather > than masking them all as -EFAULT by the callee below? Thanks, ok. let me return negative errno on error. Thanks! Yan > > > +} > > + > > +static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t iova, > > + void *data, size_t count, bool write) > > +{ > > + struct vfio_iommu *iommu = iommu_data; > > + int ret = 0; > > + size_t done = 0; > > + > > + mutex_lock(&iommu->lock); > > + while (count > 0) { > > + done = vfio_iommu_type1_dma_rw_chunk(iommu, iova, data, > > + count, write); > > + if (!done) { > > + ret = -EFAULT; > > + break; > > + } > > + > > + count -= done; > > + data += done; > > + iova += done; > > + } > > + > > + mutex_unlock(&iommu->lock); > > + return ret; > > +} > > + > > static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = { > > .name = "vfio-iommu-type1", > > .owner = THIS_MODULE, > > @@ -2338,6 +2414,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = { > > .unpin_pages = vfio_iommu_type1_unpin_pages, > > .register_notifier = vfio_iommu_type1_register_notifier, > > .unregister_notifier = vfio_iommu_type1_unregister_notifier, > > + .dma_rw = vfio_iommu_type1_dma_rw, > > }; > > > > static int __init vfio_iommu_type1_init(void) > > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > > index 2e1fa0c7396f..fea0cb1e61d2 100644 > > --- a/include/linux/vfio.h > > +++ b/include/linux/vfio.h > > @@ -82,6 +82,8 @@ struct vfio_iommu_driver_ops { > > struct notifier_block *nb); > > int (*unregister_notifier)(void *iommu_data, > > struct notifier_block *nb); > > + int (*dma_rw)(void *iommu_data, dma_addr_t iova, > > + void *data, size_t count, bool write); > > }; > > > > extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops); > > @@ -109,6 +111,9 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, > > extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, > > int npage); > > > > +extern int vfio_dma_rw(struct vfio_group *group, dma_addr_t iova, void *data, > > + size_t len, bool write); > > + > > /* each type has independent events */ > > enum vfio_notify_type { > > VFIO_IOMMU_NOTIFY = 0, >