Re: [PATCH 06/10] vfio-iommufd: Allow iommufd to be used in place of a container fd

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On 2022/10/26 02:50, Jason Gunthorpe wrote:
This makes VFIO_GROUP_SET_CONTAINER accept both a vfio container FD and an
iommufd.

In iommufd mode an IOAS will exist after the SET_CONTAINER, but it will
not be attached to any groups.

is there any special reason that we cannot attach the IOAS in the SET
container phase or SET_IOMMU phase?


 From a VFIO perspective this means that the VFIO_GROUP_GET_STATUS and
VFIO_GROUP_FLAGS_VIABLE works subtly differently. With the container FD
the iommu_group_claim_dma_owner() is done during SET_CONTAINER but for
IOMMFD this is done during VFIO_GROUP_GET_DEVICE_FD. Meaning that

s/IOMMFD/IOMMUFD

VFIO_GROUP_FLAGS_VIABLE could be set but GET_DEVICE_FD will fail due to
viability.

As GET_DEVICE_FD can fail for many reasons already this is not expected to
be a meaningful difference.

Reorganize the tests for if the group has an assigned container or iommu
into a vfio_group_has_iommu() function and consolidate all the duplicated
WARN_ON's etc related to this.

Call container functions only if a container is actually present on the
group.

Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
  drivers/vfio/Kconfig     |  1 +
  drivers/vfio/container.c |  7 ++--
  drivers/vfio/vfio.h      |  2 ++
  drivers/vfio/vfio_main.c | 76 ++++++++++++++++++++++++++++++++--------
  4 files changed, 69 insertions(+), 17 deletions(-)

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index 86c381ceb9a1e9..1118d322eec97d 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -2,6 +2,7 @@
  menuconfig VFIO
  	tristate "VFIO Non-Privileged userspace driver framework"
  	select IOMMU_API
+	depends on IOMMUFD || !IOMMUFD
  	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
  	select INTERVAL_TREE
  	help
diff --git a/drivers/vfio/container.c b/drivers/vfio/container.c
index d97747dfb05d02..8772dad6808539 100644
--- a/drivers/vfio/container.c
+++ b/drivers/vfio/container.c
@@ -516,8 +516,11 @@ int vfio_group_use_container(struct vfio_group *group)
  {
  	lockdep_assert_held(&group->group_lock);
- if (!group->container || !group->container->iommu_driver ||
-	    WARN_ON(!group->container_users))
+	/*
+	 * The container fd has been assigned with VFIO_GROUP_SET_CONTAINER but
+	 * VFIO_SET_IOMMU hasn't been done yet.
+	 */
+	if (!group->container->iommu_driver)
  		return -EINVAL;
if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index 247590334e14b0..985e13d52989ca 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -10,6 +10,7 @@
  #include <linux/cdev.h>
  #include <linux/module.h>
+struct iommufd_ctx;
  struct iommu_group;
  struct vfio_device;
  struct vfio_container;
@@ -60,6 +61,7 @@ struct vfio_group {
  	struct kvm			*kvm;
  	struct file			*opened_file;
  	struct blocking_notifier_head	notifier;
+	struct iommufd_ctx		*iommufd;
  };
/* events for the backend driver notify callback */
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index a8d1fbfcc3ddad..cf0ea744de931e 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -35,6 +35,7 @@
  #include <linux/pm_runtime.h>
  #include <linux/interval_tree.h>
  #include <linux/iova_bitmap.h>
+#include <linux/iommufd.h>
  #include "vfio.h"
#define DRIVER_VERSION "0.3"
@@ -665,6 +666,16 @@ EXPORT_SYMBOL_GPL(vfio_unregister_group_dev);
  /*
   * VFIO Group fd, /dev/vfio/$GROUP
   */
+static bool vfio_group_has_iommu(struct vfio_group *group)
+{
+	lockdep_assert_held(&group->group_lock);
+	if (!group->container)
+		WARN_ON(group->container_users);
+	else
+		WARN_ON(!group->container_users);
+	return group->container || group->iommufd;
+}
+
  /*
   * VFIO_GROUP_UNSET_CONTAINER should fail if there are other users or
   * if there was no container to unset.  Since the ioctl is called on
@@ -676,15 +687,21 @@ static int vfio_group_ioctl_unset_container(struct vfio_group *group)
  	int ret = 0;
mutex_lock(&group->group_lock);
-	if (!group->container) {
+	if (!vfio_group_has_iommu(group)) {
  		ret = -EINVAL;
  		goto out_unlock;
  	}
-	if (group->container_users != 1) {
-		ret = -EBUSY;
-		goto out_unlock;
+	if (group->container) {
+		if (group->container_users != 1) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+		vfio_group_detach_container(group);
+	}
+	if (group->iommufd) {
+		iommufd_ctx_put(group->iommufd);
+		group->iommufd = NULL;
  	}
-	vfio_group_detach_container(group);
out_unlock:
  	mutex_unlock(&group->group_lock);
@@ -695,6 +712,7 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
  					  int __user *arg)
  {
  	struct vfio_container *container;
+	struct iommufd_ctx *iommufd;
  	struct fd f;
  	int ret;
  	int fd;
@@ -707,7 +725,7 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
  		return -EBADF;
mutex_lock(&group->group_lock);
-	if (group->container || WARN_ON(group->container_users)) {
+	if (vfio_group_has_iommu(group)) {
  		ret = -EINVAL;
  		goto out_unlock;
  	}
@@ -717,12 +735,23 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
  	}
container = vfio_container_from_file(f.file);
-	ret = -EINVAL;
  	if (container) {
  		ret = vfio_container_attach_group(container, group);
  		goto out_unlock;
  	}
+ iommufd = iommufd_ctx_from_file(f.file);
+	if (!IS_ERR(iommufd)) {
+		u32 ioas_id;
+
+		group->iommufd = iommufd;
+		ret = iommufd_vfio_compat_ioas_id(iommufd, &ioas_id);
+		goto out_unlock;
+	}
+
+	/* The FD passed is not recognized. */
+	ret = -EBADF;
+
  out_unlock:
  	mutex_unlock(&group->group_lock);
  	fdput(f);
@@ -752,9 +781,16 @@ static int vfio_device_first_open(struct vfio_device *device)
  	 * it during close_device.
  	 */
  	mutex_lock(&device->group->group_lock);
-	ret = vfio_group_use_container(device->group);
-	if (ret)
+	if (!vfio_group_has_iommu(device->group)) {
+		ret = -EINVAL;
  		goto err_module_put;
+	}
+
+	if (device->group->container) {
+		ret = vfio_group_use_container(device->group);
+		if (ret)
+			goto err_module_put;
+	}
device->kvm = device->group->kvm;
  	if (device->ops->open_device) {
@@ -762,14 +798,16 @@ static int vfio_device_first_open(struct vfio_device *device)
  		if (ret)
  			goto err_container;
  	}
-	vfio_device_container_register(device);
+	if (device->group->container)
+		vfio_device_container_register(device);
  	mutex_unlock(&device->group->group_lock);
  	return 0;
err_container:
-	vfio_group_unuse_container(device->group);
-err_module_put:
+	if (device->group->container)
+		vfio_group_unuse_container(device->group);
  	device->kvm = NULL;
+err_module_put:
  	mutex_unlock(&device->group->group_lock);
  	module_put(device->dev->driver->owner);
  	return ret;
@@ -780,11 +818,13 @@ static void vfio_device_last_close(struct vfio_device *device)
  	lockdep_assert_held(&device->dev_set->lock);
mutex_lock(&device->group->group_lock);
-	vfio_device_container_unregister(device);
+	if (device->group->container)
+		vfio_device_container_unregister(device);
  	if (device->ops->close_device)
  		device->ops->close_device(device);
  	device->kvm = NULL;
-	vfio_group_unuse_container(device->group);
+	if (device->group->container)
+		vfio_group_unuse_container(device->group);
  	mutex_unlock(&device->group->group_lock);
  	module_put(device->dev->driver->owner);
  }
@@ -900,7 +940,7 @@ static int vfio_group_ioctl_get_status(struct vfio_group *group,
  		return -ENODEV;
  	}
- if (group->container)
+	if (group->container || group->iommufd)
  		status.flags |= VFIO_GROUP_FLAGS_CONTAINER_SET |
  				VFIO_GROUP_FLAGS_VIABLE;
  	else if (!iommu_group_dma_owner_claimed(group->iommu_group))
@@ -983,6 +1023,10 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep)
  	WARN_ON(group->notifier.head);
  	if (group->container)
  		vfio_group_detach_container(group);
+	if (group->iommufd) {
+		iommufd_ctx_put(group->iommufd);
+		group->iommufd = NULL;
+	}
  	group->opened_file = NULL;
  	mutex_unlock(&group->group_lock);
  	return 0;
@@ -1879,6 +1923,8 @@ static void __exit vfio_cleanup(void)
  module_init(vfio_init);
  module_exit(vfio_cleanup);
+MODULE_IMPORT_NS(IOMMUFD);
+MODULE_IMPORT_NS(IOMMUFD_VFIO);
  MODULE_VERSION(DRIVER_VERSION);
  MODULE_LICENSE("GPL v2");
  MODULE_AUTHOR(DRIVER_AUTHOR);

--
Regards,
Yi Liu



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