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Mon, 24 Feb 2020 19:14:45 +0000 (UTC) Received: from w520.home (ovpn-116-28.phx2.redhat.com [10.3.116.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9F31D5D9CD; Mon, 24 Feb 2020 19:14:42 +0000 (UTC) Date: Mon, 24 Feb 2020 12:14:42 -0700 From: Alex Williamson To: Yan Zhao Cc: zhenyuw@linux.intel.com, intel-gvt-dev@lists.freedesktop.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, kevin.tian@intel.com, peterx@redhat.com Subject: Re: [PATCH v3 2/7] vfio: introduce vfio_dma_rw to read/write a range of IOVAs Message-ID: <20200224121442.297a9931@w520.home> In-Reply-To: <20200224084715.31753-1-yan.y.zhao@intel.com> References: <20200224084350.31574-1-yan.y.zhao@intel.com> <20200224084715.31753-1-yan.y.zhao@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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, Alex > +} > + > +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,