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Fri, 20 Mar 2020 15:40:41 +0000 (UTC) Received: from w520.home (ovpn-112-162.phx2.redhat.com [10.3.112.162]) by smtp.corp.redhat.com (Postfix) with ESMTP id AC0BD91297; Fri, 20 Mar 2020 15:40:39 +0000 (UTC) Date: Fri, 20 Mar 2020 09:40:39 -0600 From: Alex Williamson To: Yan Zhao Subject: Re: [PATCH v14 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200320094039.4d99408d@w520.home> In-Reply-To: <20200320083529.GA5456@joy-OptiPlex-7040> References: <1584560474-19946-1-git-send-email-kwankhede@nvidia.com> <1584560474-19946-6-git-send-email-kwankhede@nvidia.com> <20200320083529.GA5456@joy-OptiPlex-7040> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 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" , "Tian, Kevin" , "Liu, Yi L" , "cjia@nvidia.com" , "kvm@vger.kernel.org" , "eskultet@redhat.com" , "Yang, Ziye" , "qemu-devel@nongnu.org" , "cohuck@redhat.com" , "shuangtai.tst@alibaba-inc.com" , "dgilbert@redhat.com" , "Wang, Zhi A" , "mlevitsk@redhat.com" , "pasic@linux.ibm.com" , "aik@ozlabs.ru" , Kirti Wankhede , "eauger@redhat.com" , "felipe@nutanix.com" , "jonathan.davies@nutanix.com" , "Liu, Changpeng" , "Ken.Xue@amd.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 20 Mar 2020 04:35:29 -0400 Yan Zhao wrote: > On Thu, Mar 19, 2020 at 03:41:12AM +0800, 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 set flag > > VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP, bitmap memory should be allocated and > > zeroed by user space application. Bitmap size and page size should be set > > by user application. > > > > Signed-off-by: Kirti Wankhede > > Reviewed-by: Neo Jia > > --- > > drivers/vfio/vfio_iommu_type1.c | 55 ++++++++++++++++++++++++++++++++++++++--- > > include/uapi/linux/vfio.h | 11 +++++++++ > > 2 files changed, 62 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > > index d6417fb02174..aa1ac30f7854 100644 > > --- a/drivers/vfio/vfio_iommu_type1.c > > +++ b/drivers/vfio/vfio_iommu_type1.c > > @@ -939,7 +939,8 @@ 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; > > @@ -990,6 +991,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > > * will be returned if these conditions are not met. The v2 interface > > * will only return success and a size of zero if there were no > > * mappings within the range. > > + * > > + * When VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP flag is set, unmap request > > + * must be for single mapping. Multiple mappings with this flag set is > > + * not supported. > > */ > > if (iommu->v2) { > > dma = vfio_find_dma(iommu, unmap->iova, 1); > > @@ -997,6 +1002,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > > ret = -EINVAL; > > goto unlock; > > } > > + > > + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > > + (dma->iova != unmap->iova || dma->size != unmap->size)) { > dma is probably NULL here! Yep, I didn't look closely enough there. This is situated right between the check to make sure we're not bisecting a mapping at the start of the unmap and the check to make sure we're not bisecting a mapping at the end of the unmap. There's no guarantee that we have a valid pointer here. The test should be in the while() loop below this code. > And this restriction on UNMAP would make some UNMAP operations of vIOMMU > fail. > > e.g. below condition indeed happens in reality. > an UNMAP ioctl comes for IOVA range from 0xff800000, of size 0x200000 > However, IOVAs in this range are mapped page by page.i.e., dma->size is 0x1000. > > Previous, this UNMAP ioctl could unmap successfully as a whole. What triggers this in the guest? Note that it's only when using the GET_DIRTY_BITMAP flag that this is restricted. Does the event you're referring to potentially occur under normal circumstances in that mode? Thanks, Alex > > + 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; > > @@ -1014,6 +1026,12 @@ 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) > > + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size, > > + bitmap->pgsize, > > + (unsigned char __user *) bitmap->data); > > + > > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > > struct vfio_iommu_type1_dma_unmap nb_unmap; > > > > @@ -2369,17 +2387,46 @@ 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; > > + uint64_t iommu_pgsize = > > + 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 043e9eafb255..a704e5380f04 100644 > > --- a/include/uapi/linux/vfio.h > > +++ b/include/uapi/linux/vfio.h > > @@ -1010,12 +1010,23 @@ 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, clear the bitmap memory by setting zero and must set size of > > + * allocated memory in vfio_bitmap.size field. One bit in bitmap > > + * represents per page, 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) > > -- > > 2.7.0 > > >