Re: [PATCH v2 10/11] vfio: Make vfio_container optionally compiled

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Nov 10, 2022 at 06:57:57AM +0000, Tian, Kevin wrote:

> > +	/*
> > +	 * Emulation for NOIMMU is imperfect in that VFIO blocks almost all
> > +	 * other ioctls. We let them keep working but they mostly fail since no
> > +	 * IOAS should exist.
> > +	 */
> > +	if (IS_ENABLED(CONFIG_VFIO_NOIOMMU) && type ==
> > VFIO_NOIOMMU_IOMMU)
> > +		return 0;
> > +
> >  	if (type != VFIO_TYPE1_IOMMU && type != VFIO_TYPE1v2_IOMMU)
> >  		return -EINVAL;
> 
> also need a check in iommufd_vfio_check_extension() so only
> VFIO_NOIOMMU_IOMMU is supported in no-iommu mode.

Mm, and some permission checks too

> > +		if (!IS_ENABLED(CONFIG_VFIO_NO_IOMMU) ||
> > +		    group->type != VFIO_NO_IOMMU) {
> > +			ret = iommufd_vfio_compat_ioas_id(iommufd,
> > &ioas_id);
> > +			if (ret) {
> > +				iommufd_ctx_put(group->iommufd);
> > +				goto out_unlock;
> > +			}
> >  		}
> 
> with above I suppose other ioctls (map/unmap/etc.) are implicitly blocked
> given get_compat_ioas() will fail in those paths. this is good.
> 
> btw vfio container requires exact match between group->type and
> container->noiommu, i.e. noiommu group can be only attached to noiommu
> container. this is another thing to be paired up.

Sure, as below

So, the missing ingredient here is somone who has the necessary device
to test dpdk? I wonder if qemu e1000 is able to do this path?

diff --git a/drivers/iommu/iommufd/vfio_compat.c b/drivers/iommu/iommufd/vfio_compat.c
index dbef3274803336..c20e55ddc9aa81 100644
--- a/drivers/iommu/iommufd/vfio_compat.c
+++ b/drivers/iommu/iommufd/vfio_compat.c
@@ -26,16 +26,35 @@ static struct iommufd_ioas *get_compat_ioas(struct iommufd_ctx *ictx)
 }
 
 /**
- * iommufd_vfio_compat_ioas_id - Return the IOAS ID that vfio should use
+ * iommufd_vfio_compat_ioas_get_id - Ensure a comat IOAS exists
+ * @ictx: Context to operate on
+ *
+ * Return the ID of the current compatability ioas. The ID can be passed into
+ * other functions that take an ioas_id.
+ */
+int iommufd_vfio_compat_ioas_get_id(struct iommufd_ctx *ictx, u32 *out_ioas_id)
+{
+	struct iommufd_ioas *ioas;
+
+	ioas = get_compat_ioas(ictx);
+	if (IS_ERR(ioas))
+		return PTR_ERR(ioas);
+	*out_ioas_id = ioas->obj.id;
+	iommufd_put_object(&ioas->obj);
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_vfio_compat_ioas_get_id, IOMMUFD_VFIO);
+
+/**
+ * iommufd_vfio_compat_ioas_create_id - Return the IOAS ID that vfio should use
  * @ictx: Context to operate on
- * @out_ioas_id: The ioas_id the caller should use
  *
  * The compatibility IOAS is the IOAS that the vfio compatibility ioctls operate
  * on since they do not have an IOAS ID input in their ABI. Only attaching a
- * group should cause a default creation of the internal ioas, this returns the
- * existing ioas if it has already been assigned somehow.
+ * group should cause a default creation of the internal ioas, this does nothing
+ * if an existing ioas has already been assigned somehow.
  */
-int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx, u32 *out_ioas_id)
+int iommufd_vfio_compat_ioas_create_id(struct iommufd_ctx *ictx)
 {
 	struct iommufd_ioas *ioas = NULL;
 	struct iommufd_ioas *out_ioas;
@@ -53,7 +72,6 @@ int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx, u32 *out_ioas_id)
 	}
 	xa_unlock(&ictx->objects);
 
-	*out_ioas_id = out_ioas->obj.id;
 	if (out_ioas != ioas) {
 		iommufd_put_object(&out_ioas->obj);
 		iommufd_object_abort(ictx, &ioas->obj);
@@ -68,7 +86,7 @@ int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx, u32 *out_ioas_id)
 	iommufd_object_finalize(ictx, &ioas->obj);
 	return 0;
 }
-EXPORT_SYMBOL_NS_GPL(iommufd_vfio_compat_ioas_id, IOMMUFD_VFIO);
+EXPORT_SYMBOL_NS_GPL(iommufd_vfio_compat_ioas_create_id, IOMMUFD_VFIO);
 
 int iommufd_vfio_ioas(struct iommufd_ucmd *ucmd)
 {
@@ -230,6 +248,9 @@ static int iommufd_vfio_check_extension(struct iommufd_ctx *ictx,
 	case VFIO_UNMAP_ALL:
 		return 1;
 
+	case VFIO_NOIOMMU_IOMMU:
+	return IS_ENABLED(CONFIG_VFIO_NOIOMMU);
+
 	case VFIO_DMA_CC_IOMMU:
 		return iommufd_vfio_cc_iommu(ictx);
 
@@ -259,6 +280,17 @@ static int iommufd_vfio_set_iommu(struct iommufd_ctx *ictx, unsigned long type)
 	struct iommufd_ioas *ioas = NULL;
 	int rc = 0;
 
+	/*
+	 * Emulation for NOIMMU is imperfect in that VFIO blocks almost all
+	 * other ioctls. We let them keep working but they mostly fail since no
+	 * IOAS should exist.
+	 */
+	if (IS_ENABLED(CONFIG_VFIO_NOIOMMU) && type == VFIO_NOIOMMU_IOMMU) {
+		if (!capable(CAP_SYS_RAWIO))
+			return -EPERM;
+		return 0;
+	}
+
 	if (type != VFIO_TYPE1_IOMMU && type != VFIO_TYPE1v2_IOMMU)
 		return -EINVAL;
 
diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index 595c7b2146f88c..daa8039da7a8fa 100644
--- a/drivers/vfio/iommufd.c
+++ b/drivers/vfio/iommufd.c
@@ -18,6 +18,21 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
 
 	lockdep_assert_held(&vdev->dev_set->lock);
 
+	if (IS_ENABLED(CONFIG_VFIO_NO_IOMMU) &&
+	    vdev->group->type == VFIO_NO_IOMMU) {
+		if (!capable(CAP_SYS_RAWIO))
+			return -EPERM;
+
+		/*
+		 * Require no compat ioas to be assigned to proceed. The basic
+		 * statement is that the user cannot have done something that
+		 * implies they expected translation to exist
+		 */
+		if (!iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id))
+			return -EPERM;
+		return 0;
+	}
+
 	/*
 	 * If the driver doesn't provide this op then it means the device does
 	 * not do DMA at all. So nothing to do.
@@ -29,7 +44,7 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
 	if (ret)
 		return ret;
 
-	ret = iommufd_vfio_compat_ioas_id(ictx, &ioas_id);
+	ret = iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id);
 	if (ret)
 		goto err_unbind;
 	ret = vdev->ops->attach_ioas(vdev, &ioas_id);
@@ -53,6 +68,10 @@ void vfio_iommufd_unbind(struct vfio_device *vdev)
 {
 	lockdep_assert_held(&vdev->dev_set->lock);
 
+	if (IS_ENABLED(CONFIG_VFIO_NO_IOMMU) &&
+	    vdev->group->type == VFIO_NO_IOMMU)
+		return;
+
 	if (vdev->ops->unbind_iommufd)
 		vdev->ops->unbind_iommufd(vdev);
 }
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index f3c48b8c45627d..b59eff30968a1e 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -747,12 +747,13 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
 
 	iommufd = iommufd_ctx_from_file(f.file);
 	if (!IS_ERR(iommufd)) {
-		u32 ioas_id;
-
-		ret = iommufd_vfio_compat_ioas_id(iommufd, &ioas_id);
-		if (ret) {
-			iommufd_ctx_put(group->iommufd);
-			goto out_unlock;
+		if (!IS_ENABLED(CONFIG_VFIO_NO_IOMMU) ||
+		    group->type != VFIO_NO_IOMMU) {
+			ret = iommufd_vfio_compat_ioas_create_id(iommufd);
+			if (ret) {
+				iommufd_ctx_put(group->iommufd);
+				goto out_unlock;
+			}
 		}
 
 		group->iommufd = iommufd;
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 7a5d64a1dae482..bf2b3ea5f90fd2 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -61,7 +61,8 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
 				unsigned long iova, unsigned long length);
 int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
 		      void *data, size_t len, unsigned int flags);
-int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx, u32 *out_ioas_id);
+int iommufd_vfio_compat_ioas_get_id(struct iommufd_ctx *ictx, u32 *out_ioas_id);
+int iommufd_vfio_compat_ioas_create_id(struct iommufd_ctx *ictx);
 #else /* !CONFIG_IOMMUFD */
 static inline struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
 {
@@ -93,8 +94,7 @@ static inline int iommufd_access_rw(struct iommufd_access *access, unsigned long
 	return -EOPNOTSUPP;
 }
 
-static inline int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx,
-					      u32 *out_ioas_id)
+static inline int iommufd_vfio_compat_ioas_create_id(struct iommufd_ctx *ictx)
 {
 	return -EOPNOTSUPP;
 }