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Fri, 13 Mar 2020 18:45:32 +0000 (UTC) Received: from x1.home (ovpn-116-28.phx2.redhat.com [10.3.116.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9A5BC61070; Fri, 13 Mar 2020 18:45:29 +0000 (UTC) Date: Fri, 13 Mar 2020 12:45:29 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH v13 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Message-ID: <20200313124529.402e01c3@x1.home> In-Reply-To: <1584035607-23166-6-git-send-email-kwankhede@nvidia.com> References: <1584035607-23166-1-git-send-email-kwankhede@nvidia.com> <1584035607-23166-6-git-send-email-kwankhede@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 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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, 12 Mar 2020 23:23:25 +0530 Kirti Wankhede wrote: > Pages, pinned by external interface for requested IO virtual address > range, might get unpinned and unmapped while migration is active and "DMA mapped pages, including those pinned by mdev vendor drivers, might get..." > device is still running, that is, in pre-copy phase while guest driver "...running. For example, in pre-copy..." > still could access those pages. Host device can write to these pages while > those were mapped. "...those pages, host device or vendor driver can dirty these mapped pages." > Such pages should be marked dirty so that after > migration guest driver should still be able to complete the operation. Complete what operation? We need to report these dirty pages in order 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. It seems like zeroed pages are no longer strictly necessary now that we require requests to match existing mappings, right? > Signed-off-by: Kirti Wankhede > Reviewed-by: Neo Jia > --- > drivers/vfio/vfio_iommu_type1.c | 63 +++++++++++++++++++++++++++++++++++++---- > include/uapi/linux/vfio.h | 12 ++++++++ > 2 files changed, 70 insertions(+), 5 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 435e84269a28..4037b82c6db0 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -976,7 +976,8 @@ static int verify_bitmap_size(unsigned long npages, unsigned long 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, > + unsigned long *bitmap) > { > uint64_t mask; > struct vfio_dma *dma, *dma_last = NULL; > @@ -1027,6 +1028,10 @@ 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); > @@ -1034,6 +1039,13 @@ 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)) { > + 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; > @@ -1051,6 +1063,11 @@ 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) > + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size, > + unmap->bitmap_pgsize, > + (unsigned char __user *) bitmap); > + > if (!RB_EMPTY_ROOT(&dma->pfn_list)) { > struct vfio_iommu_type1_dma_unmap nb_unmap; > > @@ -1076,6 +1093,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > &nb_unmap); > goto again; > } > + > unmapped += dma->size; > vfio_remove_dma(iommu, dma); > } Spurious white space. > @@ -2406,22 +2424,57 @@ 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; > + unsigned long *bitmap = NULL; Shouldn't this have a __user attribute? Also long doesn't seem the right type. void would be ok here. > + long ret, bsize; > > 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_pgsizes = vfio_pgsize_bitmap(iommu); > + uint64_t iommu_pgmask = > + ((uint64_t)1 << __ffs(iommu_pgsizes)) - 1; > + Need to test that unmap.argsz includes this. > + if (copy_from_user(&unmap, (void __user *)arg, > + sizeof(unmap))) > + return -EFAULT; > + > + pgshift = __ffs(unmap.bitmap_pgsize); > + > + if (((unmap.bitmap_pgsize - 1) & iommu_pgmask) != > + (unmap.bitmap_pgsize - 1)) > + return -EINVAL; > + > + if ((unmap.bitmap_pgsize & iommu_pgsizes) != > + unmap.bitmap_pgsize) > + return -EINVAL; > + if (unmap.iova + unmap.size < unmap.iova) > + return -EINVAL; > + if (!access_ok((void __user *)unmap.bitmap, > + unmap.bitmap_size)) > + return -EINVAL; These tests should be identical to the previous patch. > + > + bsize = verify_bitmap_size(unmap.size >> pgshift, > + unmap.bitmap_size); > + if (bsize < 0) > + return bsize; > + bitmap = unmap.bitmap; > + } > + > + ret = vfio_dma_do_unmap(iommu, &unmap, bitmap); > if (ret) > return ret; > > - return copy_to_user((void __user *)arg, &unmap, minsz) ? > + ret = copy_to_user((void __user *)arg, &unmap, minsz) ? > -EFAULT : 0; > + return ret; Why? Leftover debugging? > } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) { > struct vfio_iommu_type1_dirty_bitmap dirty; > uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START | > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index 02d555cc7036..12b2094f887e 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -1004,12 +1004,24 @@ struct vfio_iommu_type1_dma_map { > * 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 should > + * allocate memory to get bitmap, clear the bitmap memory by setting zero and > + * should set size of allocated memory in bitmap_size field. One bit in bitmap > + * represents per page , page of user provided page size in 'bitmap_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 bitmap. > */ > 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) */ > + __u64 bitmap_pgsize; /* page size for bitmap */ > + __u64 bitmap_size; /* in bytes */ > + void __user *bitmap; /* one bit per page */ This suggests to me that we should further split struct vfio_iommu_type1_dirty_bitmap_get so that we can use the same sub-structure here. For example: struct vfio_bitmap { __u64 pgsize; __u64 size; __u64 __user *data; }; Note we still have a void* rather than __u64* in original above. Also, why wouldn't we take the same data[] approach as the previous patch, defining this as the data when the GET_DIRTY_BITMAP flag is set? Previous patch would be updated to something like: struct vfio_iommu_type1_dirty_bitmap_get { __u64 iova; __u64 size; struct vfio_bitmap bitmap; }; > }; > > #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)