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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 C8626C28CBC for ; Wed, 6 May 2020 22:26:07 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8DA3A20753 for ; Wed, 6 May 2020 22:26:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RGZP43EC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DA3A20753 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56202 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jWSUQ-00005f-Px for qemu-devel@archiver.kernel.org; Wed, 06 May 2020 18:26:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33740) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jWSTo-00083H-8o for qemu-devel@nongnu.org; Wed, 06 May 2020 18:25:28 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:52030 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jWSTl-00033g-Te for qemu-devel@nongnu.org; Wed, 06 May 2020 18:25:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588803923; 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=E3U+gsBilIHMZ4uPxCytIc/RMmv38zJeb/Hi2ox4QaI=; b=RGZP43ECvlygbzmatp6o94TYzwf6ONRUJTelu4+RdXdQcuv4hrzKkUaxsQtqynDjgkqI0u iHpPhoHB7JX65bkPC6KZPc/xPDAOPoT6SIxd9sQ6cdObfeWqZbkDC4WezK9Wiggci6NRX8 OsTf2FFSKyjShF2QzuWmfqAxWfQAT2w= 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-151-_N0XuafGPgq7bt-1I3bQFQ-1; Wed, 06 May 2020 18:25:19 -0400 X-MC-Unique: _N0XuafGPgq7bt-1I3bQFQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4CB5E460; Wed, 6 May 2020 22:25:17 +0000 (UTC) Received: from w520.home (ovpn-113-95.phx2.redhat.com [10.3.113.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3D03F1001920; Wed, 6 May 2020 22:25:14 +0000 (UTC) Date: Wed, 6 May 2020 16:25:11 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH Kernel v18 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200506162511.032bb1e6@w520.home> In-Reply-To: <1588607939-26441-6-git-send-email-kwankhede@nvidia.com> References: <1588607939-26441-1-git-send-email-kwankhede@nvidia.com> <1588607939-26441-6-git-send-email-kwankhede@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Received-SPF: pass client-ip=207.211.31.120; envelope-from=alex.williamson@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/06 16:22:47 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com, yi.l.liu@intel.com, cjia@nvidia.com, kvm@vger.kernel.org, eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com, shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com, jonathan.davies@nutanix.com, yan.y.zhao@intel.com, changpeng.liu@intel.com, Ken.Xue@amd.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 4 May 2020 21:28:57 +0530 Kirti Wankhede wrote: > DMA mapped pages, including those pinned by mdev vendor drivers, might > get unpinned and unmapped while migration is active and device is still > running. For example, in pre-copy phase while guest driver could access > those pages, host device or vendor driver can dirty these mapped pages. > Such pages should be marked dirty so as to maintain memory consistency > for a user making use of dirty page tracking. > > To get bitmap during unmap, user should allocate memory for bitmap, set > size of allocated memory, set page size to be considered for bitmap and > set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP. > > Signed-off-by: Kirti Wankhede > Reviewed-by: Neo Jia > --- > drivers/vfio/vfio_iommu_type1.c | 84 +++++++++++++++++++++++++++++++++++++++-- > include/uapi/linux/vfio.h | 10 +++++ > 2 files changed, 90 insertions(+), 4 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 01dcb417836f..8b27faf1ec38 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -983,12 +983,14 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) > } > > static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > - struct vfio_iommu_type1_dma_unmap *unmap) > + struct vfio_iommu_type1_dma_unmap *unmap, > + struct vfio_bitmap *bitmap) > { > uint64_t mask; > struct vfio_dma *dma, *dma_last = NULL; > size_t unmapped = 0; > int ret = 0, retries = 0; > + unsigned long *final_bitmap = NULL, *temp_bitmap = NULL; > > mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1; > > @@ -1041,6 +1043,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > ret = -EINVAL; > goto unlock; > } > + > dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0); > if (dma && dma->iova + dma->size != unmap->iova + unmap->size) { > ret = -EINVAL; > @@ -1048,6 +1051,22 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > } > } > > + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > + iommu->dirty_page_tracking) { Why do we even accept VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP when not dirty page tracking rather than returning -EINVAL? It would simplify things here to reject it at the ioctl and silently ignoring a flag is rarely if ever the right approach. > + final_bitmap = kvzalloc(bitmap->size, GFP_KERNEL); > + if (!final_bitmap) { > + ret = -ENOMEM; > + goto unlock; > + } > + > + temp_bitmap = kvzalloc(bitmap->size, GFP_KERNEL); > + if (!temp_bitmap) { > + ret = -ENOMEM; > + kfree(final_bitmap); > + goto unlock; > + } YIKES! So the user can instantly trigger the kernel to internally allocate 2 x 256MB, regardless of how much they can actually map. > + } > + > while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) { > if (!iommu->v2 && unmap->iova > dma->iova) > break; > @@ -1058,6 +1077,24 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > if (dma->task->mm != current->mm) > break; > > + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > + iommu->dirty_page_tracking) { > + unsigned long pgshift = __ffs(bitmap->pgsize); > + unsigned int npages = dma->size >> pgshift; > + unsigned int shift; > + > + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size, > + bitmap->pgsize, (u64 *)temp_bitmap); vfio_iova_dirty_bitmap() takes a __user bitmap, we're doing copy_to_user() on a kernel allocated buffer??? > + > + shift = (dma->iova - unmap->iova) >> pgshift; > + if (shift) > + bitmap_shift_left(temp_bitmap, temp_bitmap, > + shift, npages); > + bitmap_or(final_bitmap, final_bitmap, temp_bitmap, > + shift + npages); > + memset(temp_bitmap, 0, bitmap->size); > + } It seems like if the per vfio_dma dirty bitmap was oversized by a long that we could shift it in place, then we'd only need one working bitmap buffer and we could size that to fit the vfio_dma (or the largest vfio_dma if we don't want to free and re-alloc for each vfio_dma). We'd need to do more copy_to/from_user()s, but we'd also avoid copying between sparse mappings (user zero'd bitmap required) and we'd have a far more reasonable memory usage. Thanks, Alex > + > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > struct vfio_iommu_type1_dma_unmap nb_unmap; > > @@ -1088,6 +1125,16 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > } > > unlock: > + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > + iommu->dirty_page_tracking && final_bitmap) { > + if (copy_to_user((void __user *)bitmap->data, final_bitmap, > + bitmap->size)) > + ret = -EFAULT; > + > + kfree(final_bitmap); > + kfree(temp_bitmap); > + } > + > mutex_unlock(&iommu->lock); > > /* Report how much was unmapped */ > @@ -2419,17 +2466,46 @@ static long vfio_iommu_type1_ioctl(void *iommu_data, > > } else if (cmd == VFIO_IOMMU_UNMAP_DMA) { > struct vfio_iommu_type1_dma_unmap unmap; > - long ret; > + struct vfio_bitmap bitmap = { 0 }; > + int ret; > > minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size); > > if (copy_from_user(&unmap, (void __user *)arg, minsz)) > return -EFAULT; > > - if (unmap.argsz < minsz || unmap.flags) > + if (unmap.argsz < minsz || > + unmap.flags & ~VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) > return -EINVAL; > > - ret = vfio_dma_do_unmap(iommu, &unmap); > + if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) { > + unsigned long pgshift; > + size_t iommu_pgsize = > + (size_t)1 << __ffs(vfio_pgsize_bitmap(iommu)); > + > + if (unmap.argsz < (minsz + sizeof(bitmap))) > + return -EINVAL; > + > + if (copy_from_user(&bitmap, > + (void __user *)(arg + minsz), > + sizeof(bitmap))) > + return -EFAULT; > + > + /* allow only min supported pgsize */ > + if (bitmap.pgsize != iommu_pgsize) > + return -EINVAL; > + if (!access_ok((void __user *)bitmap.data, bitmap.size)) > + return -EINVAL; > + > + pgshift = __ffs(bitmap.pgsize); > + ret = verify_bitmap_size(unmap.size >> pgshift, > + bitmap.size); > + if (ret) > + return ret; > + > + } > + > + ret = vfio_dma_do_unmap(iommu, &unmap, &bitmap); > if (ret) > return ret; > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index 5f359c63f5ef..e3cbf8b78623 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -1048,12 +1048,22 @@ struct vfio_bitmap { > * field. No guarantee is made to the user that arbitrary unmaps of iova > * or size different from those used in the original mapping call will > * succeed. > + * VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP should be set to get dirty bitmap > + * before unmapping IO virtual addresses. When this flag is set, user must > + * provide data[] as structure vfio_bitmap. User must allocate memory to get > + * bitmap and must set size of allocated memory in vfio_bitmap.size field. > + * A bit in bitmap represents one page of user provided page size in 'pgsize', > + * consecutively starting from iova offset. Bit set indicates page at that > + * offset from iova is dirty. Bitmap of pages in the range of unmapped size is > + * returned in vfio_bitmap.data > */ > struct vfio_iommu_type1_dma_unmap { > __u32 argsz; > __u32 flags; > +#define VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP (1 << 0) > __u64 iova; /* IO virtual address */ > __u64 size; /* Size of mapping (bytes) */ > + __u8 data[]; > }; > > #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)