[PATCH] vfio: Support VFIO_NOIOMMU with iommufd

Jason Gunthorpe
2023-01-09T14:23:06Z

Add a small amount of emulation to vfio_compat to accept the SET_IOMMU
to VFIO_NOIOMMU_IOMMU and have vfio just ignore iommufd if it is working
on a no-iommu enabled device.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/iommufd/Kconfig | 2 +-
drivers/iommu/iommufd/vfio_compat.c | 46 ++++++++++++++++++++++++-----
drivers/vfio/group.c | 13 ++++----
drivers/vfio/iommufd.c | 21 ++++++++++++-
include/linux/iommufd.h | 6 ++--
5 files changed, 70 insertions(+), 18 deletions(-)

This needs a testing confirmation with dpdk to go forward, thanks

diff --git a/drivers/iommu/iommufd/Kconfig b/drivers/iommu/iommufd/Kconfig
index 8306616b6d8198..ada693ea51a78e 100644
--- a/drivers/iommu/iommufd/Kconfig
+++ b/drivers/iommu/iommufd/Kconfig
@@ -23,7 +23,7 @@ config IOMMUFD_VFIO_CONTAINER
removed.

IOMMUFD VFIO container emulation is known to lack certain features
- of the native VFIO container, such as no-IOMMU support, peer-to-peer
+ of the native VFIO container, such as peer-to-peer
DMA mapping, PPC IOMMU support, as well as other potentially
undiscovered gaps. This option is currently intended for the
purpose of testing IOMMUFD with unmodified userspace supporting VFIO
diff --git a/drivers/iommu/iommufd/vfio_compat.c b/drivers/iommu/iommufd/vfio_compat.c
index 3ceca0e8311c39..6c8e5dc1c221f4 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 compatibility 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)
{
@@ -235,6 +253,9 @@ 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);

@@ -264,6 +285,17 @@ 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/group.c b/drivers/vfio/group.c
index bb24b2f0271e03..0f2a483a1f3bdb 100644
--- a/drivers/vfio/group.c
+++ b/drivers/vfio/group.c
@@ -133,12 +133,13 @@ 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/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index 4f82a6fa7c6c7f..da50feb24b6e1d 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);
@@ -52,6 +67,10 @@ 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/include/linux/iommufd.h b/include/linux/iommufd.h
index 650d45629647a7..9d1afd417215d0 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -57,7 +57,8 @@ 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)
{
@@ -89,8 +90,7 @@ 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;
}

base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
--
2.39.0