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=-6.8 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,URIBL_BLOCKED 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 16668C433E0 for ; Thu, 14 May 2020 13:22:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF8E62065D for ; Thu, 14 May 2020 13:22:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KaBsUi9/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726056AbgENNWZ (ORCPT ); Thu, 14 May 2020 09:22:25 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:39546 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726011AbgENNWZ (ORCPT ); Thu, 14 May 2020 09:22:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589462542; 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=MdFatK4dMmg5r9h9ucfSIgBeMZlPxRK7IWuruD5QQV8=; b=KaBsUi9/eQHRXsm8ARbH3A/aJn+DFWX7ny63q88jrFoB6cXtGNtI64myCe/XmMIA/hQLMV m6L7f7uhsZcMwTnCkxfZqbJ2wrGrA6UQ+Q/PcTTlKiyIG897uXFyxHFLbfg+9nFoaCRvIS zxCRzo6t1ERHIpDIEwq/M543sBYNFpY= 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-162-ZceqEK4cOhyUTgfFAGxufw-1; Thu, 14 May 2020 09:22:09 -0400 X-MC-Unique: ZceqEK4cOhyUTgfFAGxufw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4D3F4EC1A0; Thu, 14 May 2020 13:22:07 +0000 (UTC) Received: from x1.home (ovpn-113-111.phx2.redhat.com [10.3.113.111]) by smtp.corp.redhat.com (Postfix) with ESMTP id 66DF781E0A; Thu, 14 May 2020 13:22:04 +0000 (UTC) Date: Thu, 14 May 2020 07:22:03 -0600 From: Alex Williamson To: Kirti Wankhede Cc: , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH Kernel v19 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200514072203.3aee3e89@x1.home> In-Reply-To: <65a90392-a140-6862-b7f2-2bddc6e71ba9@nvidia.com> References: <1589400279-28522-1-git-send-email-kwankhede@nvidia.com> <1589400279-28522-7-git-send-email-kwankhede@nvidia.com> <20200513230747.0d2f3bc3@x1.home> <65a90392-a140-6862-b7f2-2bddc6e71ba9@nvidia.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 14 May 2020 11:02:33 +0530 Kirti Wankhede wrote: > On 5/14/2020 10:37 AM, Alex Williamson wrote: > > On Thu, 14 May 2020 01:34:37 +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 | 102 +++++++++++++++++++++++++++++++++++----- > >> include/uapi/linux/vfio.h | 10 ++++ > >> 2 files changed, 99 insertions(+), 13 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 469b09185b83..4358be26ff80 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -195,11 +195,15 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > >> static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, size_t pgsize) > >> { > >> uint64_t npages = dma->size / pgsize; > >> + size_t bitmap_size; > >> > >> if (npages > DIRTY_BITMAP_PAGES_MAX) > >> return -EINVAL; > >> > >> - dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); > >> + /* Allocate extra 64 bits which are used for bitmap manipulation */ > >> + bitmap_size = DIRTY_BITMAP_BYTES(npages) + sizeof(u64); > >> + > >> + dma->bitmap = kvzalloc(bitmap_size, GFP_KERNEL); > >> if (!dma->bitmap) > >> return -ENOMEM; > >> > >> @@ -979,23 +983,25 @@ 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; > >> + size_t unmapped = 0, pgsize; > >> + int ret = 0, retries = 0, cnt = 0; > >> + unsigned long pgshift, shift = 0, leftover; > >> > >> mutex_lock(&iommu->lock); > >> > >> - mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1; > >> + pgshift = __ffs(iommu->pgsize_bitmap); > >> + pgsize = (size_t)1 << pgshift; > >> > >> - if (unmap->iova & mask) { > >> + if (unmap->iova & (pgsize - 1)) { > >> ret = -EINVAL; > >> goto unlock; > >> } > >> > >> - if (!unmap->size || unmap->size & mask) { > >> + if (!unmap->size || unmap->size & (pgsize - 1)) { > >> ret = -EINVAL; > >> goto unlock; > >> } > >> @@ -1006,9 +1012,15 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> goto unlock; > >> } > >> > >> - WARN_ON(mask & PAGE_MASK); > >> -again: > >> + /* When dirty tracking is enabled, allow only min supported pgsize */ > >> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >> + (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { > >> + ret = -EINVAL; > >> + goto unlock; > >> + } > >> > >> + WARN_ON((pgsize - 1) & PAGE_MASK); > >> +again: > >> /* > >> * vfio-iommu-type1 (v1) - User mappings were coalesced together to > >> * avoid tracking individual mappings. This means that the granularity > >> @@ -1046,6 +1058,7 @@ 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; > >> @@ -1063,6 +1076,39 @@ 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) && > >> + (dma_last != dma)) { > >> + unsigned int nbits = dma->size >> pgshift; > >> + int curr_lcnt = nbits / BITS_PER_LONG; > >> + > >> + /* > >> + * mark all pages dirty if all pages are pinned and > >> + * mapped. > >> + */ > >> + if (dma->iommu_mapped) > >> + bitmap_set(dma->bitmap, 0, nbits); > >> + > >> + if (shift) { > >> + bitmap_shift_left(dma->bitmap, dma->bitmap, > >> + shift, nbits + shift); > >> + bitmap_or(dma->bitmap, dma->bitmap, &leftover, > >> + shift); > >> + nbits += shift; > >> + curr_lcnt = nbits / BITS_PER_LONG; > >> + } > >> + > >> + if (copy_to_user((void __user *)bitmap->data + cnt, > >> + dma->bitmap, curr_lcnt * sizeof(u64))) { > >> + ret = -EFAULT; > >> + break; > >> + } > >> + > >> + shift = nbits % BITS_PER_LONG; > >> + if (shift) > >> + leftover = *(u64 *)(dma->bitmap + curr_lcnt); > >> + cnt += curr_lcnt; > >> + } > > > > I don't think this works. Let's say for example we have separate > > single page mappings at 4K and 12K (both dirty) and the user asked to > > unmap the range 0 - 16K. > > Unmap range should include adjacent mapped ranges, right? Not required. > In your example, if user asks for range 0-16k but mapping at 0 wasn't > done, then this unmap would fail before even reaching control here. Nope, that's supported. > There is a check which makes sure that mapping for start of range exist: > > dma = vfio_find_dma(iommu, unmap->iova, 1); > if (dma && dma->iova != unmap->iova) { > ret = -EINVAL; > goto unlock; > } if (dma && ... > There is a check which makes sure that mapping for last address of range > exist: > dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0); > if (dma && dma->iova + dma->size != unmap->iova + unmap->size) { > ret = -EINVAL; > goto unlock; > } if (dma && ... These are the tests that require an unmap request not _bisect_ a mapping, both tests are preceded by a check of if we found a mapping at that address, not a requirement that there be a mapping at that address, nor a requirement that mappings are consecutive across the unmap range. A user can absolutely call unmap with iova = 0, size = S64_MAX to clear a massive chunk of the address space. > Then current implementation should work. Even if I change my example that the user requested an unmap of 4K-16K with 4K mappings at 4K and 12K, the bitmap returned would have bits 0 & 1 set rather than bits 0 & 2, which is still incorrect. Thanks, Alex > > We find the mapping at 4K, shift is zero, cnt > > is zero, so we copy the bitmap with the zero bit set to the user > > buffer. We're already wrong because we've just indicated the page at > > zero is dirty and there isn't a page at zero. shift now becomes 1 and > > leftover is a bitmap with bit zero set. > > > > We move on to the next page @12K. We shift this bitmap by 1. We OR in > > our leftover and again copy out to the user buffer. We end up with a > > user bitmap with bits zero and one set, when we should have had bits 1 > > and 3 set, we're essentially coalescing the mappings. > > > > As I see it, shift needs to be calculated as the offset from the start > > of the user requested unmap buffer and I think an easier approach to > > handle the leftover bits preceding the shift is to copy it back out of > > the user buffer. > > > > For example, shift should be: > > > > ((dma->iova - unmap->iova) >> pgshift) % BITS_PER_LONG > > > > This would give us a shift of 1 and 3 respectively for our mappings, > > which is correct. > > > > Since our shifts are non-zero, we then need to collect the preceding > > leftovers, which is always going to be: > > > > copy_from_user(&leftover, bitmap->data + > > ((dma->iova - unmap->iova) >> pgshift) / BITS_PER_LONG, > > sizeof(leftover)); > > > > I don't think the curr_lcnt calculation for the copy-out is correct > > either, mappings are not required to be a multiple of BITS_PER_LONG > > pages, so we're truncating the size. > > > > So we have: > > > > bit_offset = (dma->iova - unmap->iova) >> pgshift; > > copy_offset = bit_offset / BITS_PER_LONG; > > shift = bit_offset % BITS_PER_LONG; > > > > if (shift) { > > bitmap_shift_left(dma->bitmap, dma->bitmap, shift, nbits + shift); > > if (copy_from_user(&leftover, bitmap->data + copy_offset, sizeof(leftover))) { > > ret = -EFAULT; > > break; > > } > > bitmap_or(dma->bitmap, dma->bitmap, &leftover, shift); > > } > > > > if (copy_to_user(bitmap->data + copy_offset, dma->bitmap, > > roundup(nbits + shift, BITS_PER_LONG)/BITS_PER_BYTE)) { > > ret = -EFAULT; > > break; > > } > > > > Also this all needs to come after the below check of the pfn_list and > > call to the blocking notifier or else we're just wasting time because > > we'll need to do it all again anyway. > > > > > >> + > >> if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > >> struct vfio_iommu_type1_dma_unmap nb_unmap; > >> > >> @@ -1093,6 +1139,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> vfio_remove_dma(iommu, dma); > >> } > >> > >> + if (!ret && (unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >> + shift) { > >> + if (copy_to_user((void __user *)bitmap->data + cnt, &leftover, > >> + sizeof(leftover))) > >> + ret = -EFAULT; > >> + } > > > > This is unnecessary with the algorithm I propose. > > > >> + > >> unlock: > >> mutex_unlock(&iommu->lock); > >> > >> @@ -2426,17 +2479,40 @@ 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; > >> + > >> + if (unmap.argsz < (minsz + sizeof(bitmap))) > >> + return -EINVAL; > >> + > >> + if (copy_from_user(&bitmap, > >> + (void __user *)(arg + minsz), > >> + sizeof(bitmap))) > >> + return -EFAULT; > >> + > >> + 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 > > > > This needs to specify a user zero'd bitmap if we're only going to fill > > it sparsely. Thanks, > > > > Alex > > > >> */ > >> 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) > > > 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,URIBL_BLOCKED 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 7ADA7C433E0 for ; Thu, 14 May 2020 13:23:45 +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 2C5742065D for ; 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Thu, 14 May 2020 13:22:07 +0000 (UTC) Received: from x1.home (ovpn-113-111.phx2.redhat.com [10.3.113.111]) by smtp.corp.redhat.com (Postfix) with ESMTP id 66DF781E0A; Thu, 14 May 2020 13:22:04 +0000 (UTC) Date: Thu, 14 May 2020 07:22:03 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH Kernel v19 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200514072203.3aee3e89@x1.home> In-Reply-To: <65a90392-a140-6862-b7f2-2bddc6e71ba9@nvidia.com> References: <1589400279-28522-1-git-send-email-kwankhede@nvidia.com> <1589400279-28522-7-git-send-email-kwankhede@nvidia.com> <20200513230747.0d2f3bc3@x1.home> <65a90392-a140-6862-b7f2-2bddc6e71ba9@nvidia.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Received-SPF: pass client-ip=205.139.110.61; envelope-from=alex.williamson@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 22:25:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] 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 Thu, 14 May 2020 11:02:33 +0530 Kirti Wankhede wrote: > On 5/14/2020 10:37 AM, Alex Williamson wrote: > > On Thu, 14 May 2020 01:34:37 +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 | 102 +++++++++++++++++++++++++++++++++++----- > >> include/uapi/linux/vfio.h | 10 ++++ > >> 2 files changed, 99 insertions(+), 13 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 469b09185b83..4358be26ff80 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -195,11 +195,15 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > >> static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, size_t pgsize) > >> { > >> uint64_t npages = dma->size / pgsize; > >> + size_t bitmap_size; > >> > >> if (npages > DIRTY_BITMAP_PAGES_MAX) > >> return -EINVAL; > >> > >> - dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); > >> + /* Allocate extra 64 bits which are used for bitmap manipulation */ > >> + bitmap_size = DIRTY_BITMAP_BYTES(npages) + sizeof(u64); > >> + > >> + dma->bitmap = kvzalloc(bitmap_size, GFP_KERNEL); > >> if (!dma->bitmap) > >> return -ENOMEM; > >> > >> @@ -979,23 +983,25 @@ 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; > >> + size_t unmapped = 0, pgsize; > >> + int ret = 0, retries = 0, cnt = 0; > >> + unsigned long pgshift, shift = 0, leftover; > >> > >> mutex_lock(&iommu->lock); > >> > >> - mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1; > >> + pgshift = __ffs(iommu->pgsize_bitmap); > >> + pgsize = (size_t)1 << pgshift; > >> > >> - if (unmap->iova & mask) { > >> + if (unmap->iova & (pgsize - 1)) { > >> ret = -EINVAL; > >> goto unlock; > >> } > >> > >> - if (!unmap->size || unmap->size & mask) { > >> + if (!unmap->size || unmap->size & (pgsize - 1)) { > >> ret = -EINVAL; > >> goto unlock; > >> } > >> @@ -1006,9 +1012,15 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> goto unlock; > >> } > >> > >> - WARN_ON(mask & PAGE_MASK); > >> -again: > >> + /* When dirty tracking is enabled, allow only min supported pgsize */ > >> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >> + (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { > >> + ret = -EINVAL; > >> + goto unlock; > >> + } > >> > >> + WARN_ON((pgsize - 1) & PAGE_MASK); > >> +again: > >> /* > >> * vfio-iommu-type1 (v1) - User mappings were coalesced together to > >> * avoid tracking individual mappings. This means that the granularity > >> @@ -1046,6 +1058,7 @@ 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; > >> @@ -1063,6 +1076,39 @@ 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) && > >> + (dma_last != dma)) { > >> + unsigned int nbits = dma->size >> pgshift; > >> + int curr_lcnt = nbits / BITS_PER_LONG; > >> + > >> + /* > >> + * mark all pages dirty if all pages are pinned and > >> + * mapped. > >> + */ > >> + if (dma->iommu_mapped) > >> + bitmap_set(dma->bitmap, 0, nbits); > >> + > >> + if (shift) { > >> + bitmap_shift_left(dma->bitmap, dma->bitmap, > >> + shift, nbits + shift); > >> + bitmap_or(dma->bitmap, dma->bitmap, &leftover, > >> + shift); > >> + nbits += shift; > >> + curr_lcnt = nbits / BITS_PER_LONG; > >> + } > >> + > >> + if (copy_to_user((void __user *)bitmap->data + cnt, > >> + dma->bitmap, curr_lcnt * sizeof(u64))) { > >> + ret = -EFAULT; > >> + break; > >> + } > >> + > >> + shift = nbits % BITS_PER_LONG; > >> + if (shift) > >> + leftover = *(u64 *)(dma->bitmap + curr_lcnt); > >> + cnt += curr_lcnt; > >> + } > > > > I don't think this works. Let's say for example we have separate > > single page mappings at 4K and 12K (both dirty) and the user asked to > > unmap the range 0 - 16K. > > Unmap range should include adjacent mapped ranges, right? Not required. > In your example, if user asks for range 0-16k but mapping at 0 wasn't > done, then this unmap would fail before even reaching control here. Nope, that's supported. > There is a check which makes sure that mapping for start of range exist: > > dma = vfio_find_dma(iommu, unmap->iova, 1); > if (dma && dma->iova != unmap->iova) { > ret = -EINVAL; > goto unlock; > } if (dma && ... > There is a check which makes sure that mapping for last address of range > exist: > dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0); > if (dma && dma->iova + dma->size != unmap->iova + unmap->size) { > ret = -EINVAL; > goto unlock; > } if (dma && ... These are the tests that require an unmap request not _bisect_ a mapping, both tests are preceded by a check of if we found a mapping at that address, not a requirement that there be a mapping at that address, nor a requirement that mappings are consecutive across the unmap range. A user can absolutely call unmap with iova = 0, size = S64_MAX to clear a massive chunk of the address space. > Then current implementation should work. Even if I change my example that the user requested an unmap of 4K-16K with 4K mappings at 4K and 12K, the bitmap returned would have bits 0 & 1 set rather than bits 0 & 2, which is still incorrect. Thanks, Alex > > We find the mapping at 4K, shift is zero, cnt > > is zero, so we copy the bitmap with the zero bit set to the user > > buffer. We're already wrong because we've just indicated the page at > > zero is dirty and there isn't a page at zero. shift now becomes 1 and > > leftover is a bitmap with bit zero set. > > > > We move on to the next page @12K. We shift this bitmap by 1. We OR in > > our leftover and again copy out to the user buffer. We end up with a > > user bitmap with bits zero and one set, when we should have had bits 1 > > and 3 set, we're essentially coalescing the mappings. > > > > As I see it, shift needs to be calculated as the offset from the start > > of the user requested unmap buffer and I think an easier approach to > > handle the leftover bits preceding the shift is to copy it back out of > > the user buffer. > > > > For example, shift should be: > > > > ((dma->iova - unmap->iova) >> pgshift) % BITS_PER_LONG > > > > This would give us a shift of 1 and 3 respectively for our mappings, > > which is correct. > > > > Since our shifts are non-zero, we then need to collect the preceding > > leftovers, which is always going to be: > > > > copy_from_user(&leftover, bitmap->data + > > ((dma->iova - unmap->iova) >> pgshift) / BITS_PER_LONG, > > sizeof(leftover)); > > > > I don't think the curr_lcnt calculation for the copy-out is correct > > either, mappings are not required to be a multiple of BITS_PER_LONG > > pages, so we're truncating the size. > > > > So we have: > > > > bit_offset = (dma->iova - unmap->iova) >> pgshift; > > copy_offset = bit_offset / BITS_PER_LONG; > > shift = bit_offset % BITS_PER_LONG; > > > > if (shift) { > > bitmap_shift_left(dma->bitmap, dma->bitmap, shift, nbits + shift); > > if (copy_from_user(&leftover, bitmap->data + copy_offset, sizeof(leftover))) { > > ret = -EFAULT; > > break; > > } > > bitmap_or(dma->bitmap, dma->bitmap, &leftover, shift); > > } > > > > if (copy_to_user(bitmap->data + copy_offset, dma->bitmap, > > roundup(nbits + shift, BITS_PER_LONG)/BITS_PER_BYTE)) { > > ret = -EFAULT; > > break; > > } > > > > Also this all needs to come after the below check of the pfn_list and > > call to the blocking notifier or else we're just wasting time because > > we'll need to do it all again anyway. > > > > > >> + > >> if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > >> struct vfio_iommu_type1_dma_unmap nb_unmap; > >> > >> @@ -1093,6 +1139,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> vfio_remove_dma(iommu, dma); > >> } > >> > >> + if (!ret && (unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >> + shift) { > >> + if (copy_to_user((void __user *)bitmap->data + cnt, &leftover, > >> + sizeof(leftover))) > >> + ret = -EFAULT; > >> + } > > > > This is unnecessary with the algorithm I propose. > > > >> + > >> unlock: > >> mutex_unlock(&iommu->lock); > >> > >> @@ -2426,17 +2479,40 @@ 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; > >> + > >> + if (unmap.argsz < (minsz + sizeof(bitmap))) > >> + return -EINVAL; > >> + > >> + if (copy_from_user(&bitmap, > >> + (void __user *)(arg + minsz), > >> + sizeof(bitmap))) > >> + return -EFAULT; > >> + > >> + 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 > > > > This needs to specify a user zero'd bitmap if we're only going to fill > > it sparsely. Thanks, > > > > Alex > > > >> */ > >> 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) > > >