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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 222BAC282DD for ; Thu, 9 Jan 2020 18:16:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF631206ED for ; Thu, 9 Jan 2020 18:16:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DI+KVUfg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388435AbgAISQm (ORCPT ); Thu, 9 Jan 2020 13:16:42 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:26334 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730866AbgAISQm (ORCPT ); Thu, 9 Jan 2020 13:16:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578593799; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PuQZ01JccUJ9Y5jwRCJ72PmwXiqdqAnX2460fvsPeis=; b=DI+KVUfgnEVvKVN0OpTvxfeOmbdtKFJbWlAluedsh6eBNtDRp+KfpNWMDeNx2XZApaOSob A9JajGwgUXQ6mOVWIdFLteKdZrEt1PfgBL/7VypRFtKxgb0SyHYfcd/8mv+ZwjKmz3KuBU Vplwst++6NtJUJX9VE732I6gS4kpgZk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-104-F7aFNrvhMs6PmI2LQyT55w-1; Thu, 09 Jan 2020 13:16:38 -0500 X-MC-Unique: F7aFNrvhMs6PmI2LQyT55w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 41EDC18B9F80; Thu, 9 Jan 2020 18:16:37 +0000 (UTC) Received: from w520.home (ovpn-116-128.phx2.redhat.com [10.3.116.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id CC09760E3E; Thu, 9 Jan 2020 18:16:36 +0000 (UTC) Date: Thu, 9 Jan 2020 11:16:36 -0700 From: Alex Williamson To: Yan Zhao Cc: zhenyuw@linux.intel.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, kevin.tian@intel.com Subject: Re: [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs Message-ID: <20200109111636.2158b24c@w520.home> In-Reply-To: <20200103010217.4201-1-yan.y.zhao@intel.com> References: <20200103010055.4140-1-yan.y.zhao@intel.com> <20200103010217.4201-1-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 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2 Jan 2020 20:02:17 -0500 Yan Zhao wrote: > vfio_iova_rw will read/write a range of userspace memory (starting form > device iova to iova + len -1) into a kenrel buffer without pinning the > userspace memory. > > TODO: vfio needs to mark the iova dirty if vfio_iova_rw(write) is > called. > > Cc: Kevin Tian > Signed-off-by: Yan Zhao > --- > drivers/vfio/vfio.c | 45 ++++++++++++++++++ > drivers/vfio/vfio_iommu_type1.c | 81 +++++++++++++++++++++++++++++++++ > include/linux/vfio.h | 5 ++ > 3 files changed, 131 insertions(+) > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index c8482624ca34..36e91e647ed5 100644 > --- a/drivers/vfio/vfio.c > +++ b/drivers/vfio/vfio.c > @@ -1961,6 +1961,51 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage) > } > EXPORT_SYMBOL(vfio_unpin_pages); > > +/* > + * Read/Write a range of userspace IOVAs for a device into/from a kernel > + * buffer without pinning the userspace memory > + * @dev [in] : device > + * @iova [in] : base IOVA of a userspace buffer > + * @data [in] : pointer to kernel buffer > + * @len [in] : kernel buffer length > + * @write : indicate read or write > + * Return error on failure or 0 on success. > + */ > +int vfio_iova_rw(struct device *dev, unsigned long iova, void *data, > + unsigned long len, bool write) Shouldn't iova be a dma_addr_t and len be a size_t? AIUI this function performs the equivalent behavior of the device itself performing a DMA. Hmm, should the interface be named vfio_dma_rw()? > +{ > + struct vfio_container *container; > + struct vfio_group *group; > + struct vfio_iommu_driver *driver; > + int ret = 0; > + > + if (!dev || !data || len <= 0) > + return -EINVAL; > + > + group = vfio_group_get_from_dev(dev); > + if (!group) > + return -ENODEV; > + > + ret = vfio_group_add_container_user(group); > + if (ret) > + goto out; > + > + container = group->container; > + driver = container->iommu_driver; > + > + if (likely(driver && driver->ops->iova_rw)) > + ret = driver->ops->iova_rw(container->iommu_data, > + iova, data, len, write); > + else > + ret = -ENOTTY; > + > + vfio_group_try_dissolve_container(group); > +out: > + vfio_group_put(group); > + return ret; > +} > +EXPORT_SYMBOL(vfio_iova_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..aee191077235 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 +2327,85 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data, > return blocking_notifier_chain_unregister(&iommu->notifier, nb); > } > > +static int next_segment(unsigned long len, int offset) > +{ > + if (len > PAGE_SIZE - offset) > + return PAGE_SIZE - offset; > + else > + return len; > +} > + > +static int vfio_iommu_type1_rw_iova_seg(struct vfio_iommu *iommu, > + unsigned long iova, void *data, > + unsigned long seg_len, > + unsigned long offset, > + bool write) > +{ > + struct mm_struct *mm; > + unsigned long vaddr; > + struct vfio_dma *dma; > + bool kthread = current->mm == NULL; > + int ret = 0; > + > + dma = vfio_find_dma(iommu, iova, PAGE_SIZE); > + if (!dma) > + return -EINVAL; > + > + mm = get_task_mm(dma->task); > + > + if (!mm) > + return -ENODEV; > + > + if (kthread) > + use_mm(mm); > + else if (current->mm != mm) { > + ret = -EINVAL; > + goto out; > + } > + > + vaddr = dma->vaddr + iova - dma->iova + offset; Parenthesis here would be useful and might prevent overflow, ie: dma->vaddr + (iova - dma->iova) + offset > + > + ret = write ? __copy_to_user((void __user *)vaddr, > + data, seg_len) : > + __copy_from_user(data, (void __user *)vaddr, > + seg_len); > + if (ret) > + ret = -EFAULT; > + > + if (kthread) > + unuse_mm(mm); > +out: > + mmput(mm); > + return ret; > +} > + > +static int vfio_iommu_type1_iova_rw(void *iommu_data, unsigned long iova, > + void *data, unsigned long len, bool write) > +{ > + struct vfio_iommu *iommu = iommu_data; > + int offset = iova & ~PAGE_MASK; > + int seg_len; > + int ret = 0; > + > + iova = iova & PAGE_MASK; > + > + mutex_lock(&iommu->lock); > + while ((seg_len = next_segment(len, offset)) > 0) { > + ret = vfio_iommu_type1_rw_iova_seg(iommu, iova, data, > + seg_len, offset, write); Why do we need to split operations at page boundaries? It seems really inefficient that at each page crossing we need to lookup the vfio_dma again (probably the same one), switch to the mm (probably the same one), and perform another copy_{to,from}_user() when potentially have everything we need to perform a larger copy. Thanks, Alex > + if (ret) > + break; > + > + offset = 0; > + len -= seg_len; > + data += seg_len; > + iova += PAGE_SIZE; > + } > + > + 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 +2418,7 @@ 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, > + .iova_rw = vfio_iommu_type1_iova_rw, > }; > > static int __init vfio_iommu_type1_init(void) > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index e42a711a2800..7bf18a31bbcf 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 (*iova_rw)(void *iommu_data, unsigned long iova, > + void *data, unsigned long len, bool write); > }; > > extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops); > @@ -107,6 +109,9 @@ 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_iova_rw(struct device *dev, unsigned long iova, void *data, > + unsigned long len, bool write); > + > /* each type has independent events */ > enum vfio_notify_type { > VFIO_IOMMU_NOTIFY = 0,