Messages in this thread | | | From | Yongji Xie <> | Date | Wed, 29 Jun 2022 18:19:31 +0800 | Subject | Re: [PATCH 5/6] vduse: Support registering userspace memory for IOTLB |
| |
On Wed, Jun 29, 2022 at 5:54 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Jun 29, 2022 at 05:26:04PM +0800, Yongji Xie wrote: > > On Wed, Jun 29, 2022 at 4:43 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > > On Wed, Jun 29, 2022 at 04:25:40PM +0800, Xie Yongji wrote: > > > > Introduce two ioctls: VDUSE_IOTLB_REG_UMEM and > > > > VDUSE_IOTLB_DEREG_UMEM to support registering > > > > and de-registering userspace memory for IOTLB > > > > in virtio-vdpa case. > > > > > > > > Now it only supports registering userspace memory > > > > for IOTLB as bounce buffer. > > > > > > > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com> > > > > --- > > > > drivers/vdpa/vdpa_user/vduse_dev.c | 138 +++++++++++++++++++++++++++++ > > > > include/uapi/linux/vduse.h | 28 ++++++ > > > > 2 files changed, 166 insertions(+) > > > > > > > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c > > > > index c47a5d9765cf..7b2ea7612da9 100644 > > > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c > > > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c > > > > @@ -21,6 +21,7 @@ > > > > #include <linux/uio.h> > > > > #include <linux/vdpa.h> > > > > #include <linux/nospec.h> > > > > +#include <linux/sched/mm.h> > > > > #include <uapi/linux/vduse.h> > > > > #include <uapi/linux/vdpa.h> > > > > #include <uapi/linux/virtio_config.h> > > > > @@ -64,6 +65,13 @@ struct vduse_vdpa { > > > > struct vduse_dev *dev; > > > > }; > > > > > > > > +struct vduse_iotlb_mem { > > > > + unsigned long iova; > > > > + unsigned long npages; > > > > + struct page **pages; > > > > + struct mm_struct *mm; > > > > +}; > > > > + > > > > struct vduse_dev { > > > > struct vduse_vdpa *vdev; > > > > struct device *dev; > > > > @@ -95,6 +103,8 @@ struct vduse_dev { > > > > u8 status; > > > > u32 vq_num; > > > > u32 vq_align; > > > > + struct vduse_iotlb_mem *iotlb_mem; > > > > + struct mutex mem_lock; > > > > }; > > > > > > > > struct vduse_dev_msg { > > > > @@ -917,6 +927,100 @@ static int vduse_dev_queue_irq_work(struct vduse_dev *dev, > > > > return ret; > > > > } > > > > > > > > +static int vduse_dev_dereg_iotlb_mem(struct vduse_dev *dev, > > > > + u64 iova, u64 size) > > > > +{ > > > > + int ret; > > > > + > > > > + mutex_lock(&dev->mem_lock); > > > > + ret = -ENOENT; > > > > + if (!dev->iotlb_mem) > > > > + goto unlock; > > > > + > > > > + ret = -EINVAL; > > > > + if (dev->iotlb_mem->iova != iova || size != dev->domain->bounce_size) > > > > + goto unlock; > > > > + > > > > + vduse_domain_remove_user_bounce_pages(dev->domain); > > > > + unpin_user_pages(dev->iotlb_mem->pages, dev->iotlb_mem->npages); > > > > > > I notice you don't mark the pages dirty. This is going to be a problem. > > > > > > > Thanks for pointing out this, I will use unpin_user_pages_dirty_lock() instead. > > > > > > + atomic64_sub(dev->iotlb_mem->npages, &dev->iotlb_mem->mm->pinned_vm); > > > > + mmdrop(dev->iotlb_mem->mm); > > > > + vfree(dev->iotlb_mem->pages); > > > > + kfree(dev->iotlb_mem); > > > > + dev->iotlb_mem = NULL; > > > > + ret = 0; > > > > +unlock: > > > > + mutex_unlock(&dev->mem_lock); > > > > + return ret; > > > > +} > > > > + > > > > +static int vduse_dev_reg_iotlb_mem(struct vduse_dev *dev, > > > > + u64 iova, u64 uaddr, u64 size) > > > > +{ > > > > + struct page **page_list = NULL; > > > > + struct vduse_iotlb_mem *mem = NULL; > > > > + long pinned = 0; > > > > + unsigned long npages, lock_limit; > > > > + int ret; > > > > + > > > > + if (size != dev->domain->bounce_size || > > > > + iova != 0 || uaddr & ~PAGE_MASK) > > > > + return -EINVAL; > > > > + > > > > + mutex_lock(&dev->mem_lock); > > > > + ret = -EEXIST; > > > > + if (dev->iotlb_mem) > > > > + goto unlock; > > > > + > > > > + ret = -ENOMEM; > > > > + npages = size >> PAGE_SHIFT; > > > > + page_list = vmalloc(array_size(npages, > > > > + sizeof(struct page *))); > > > > > > Is this basically trying to do a vmalloc with userspace-controlled size? > > > That's an easy DOS vector. > > > > > > > We already checked the size before. The size must equal to (64MB >> > > PAGE_SHIFT) now. > > That's not a small amount. Can this be accounted e.g. through cgroups at least? >
Make sense, will use __vmalloc(__GFP_ACCOUNT) instead.
> > > > + mem = kzalloc(sizeof(*mem), GFP_KERNEL); > > > > + if (!page_list || !mem) > > > > + goto unlock; > > > > + > > > > + mmap_read_lock(current->mm); > > > > + > > > > + lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK)); > > > > + if (npages + atomic64_read(¤t->mm->pinned_vm) > lock_limit) > > > > + goto out; > > > > + > > > > + pinned = pin_user_pages(uaddr, npages, FOLL_LONGTERM | FOLL_WRITE, > > > > + page_list, NULL); > > > > + if (pinned != npages) { > > > > + ret = pinned < 0 ? pinned : -ENOMEM; > > > > + goto out; > > > > + } > > > > > > > > > This is a popular approach but it's problematic if multiple > > > devices try to pin the same page. > > > > Do you mean the data would be corrupted if multiple devices use the > > same page as bounce buffer? This is indeed a problem. > > No i mean you decrement the lock twice. Question is can two bounce > buffers share a page? >
I think we can't. I will find a way to prevent it.
Thanks, Yongji
| |