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

Yi Liu
2022-11-02T07:28:15Z

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@nvidia.com>
> ---
> 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