On 27/2/23 22:11, Yi Liu wrote:
This adds ioctl for userspace to bind device cdev fd to iommufd.
VFIO_DEVICE_BIND_IOMMUFD: bind device to an iommufd, hence gain DMA
control provided by the iommufd. open_device
op is called after bind_iommufd op.
VFIO no iommu mode is indicated by passing
a negative iommufd value.
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
drivers/vfio/device_cdev.c | 146 +++++++++++++++++++++++++++++++++++++
drivers/vfio/vfio.h | 17 ++++-
drivers/vfio/vfio_main.c | 54 ++++++++++++--
include/linux/iommufd.h | 6 ++
include/uapi/linux/vfio.h | 34 +++++++++
5 files changed, 248 insertions(+), 9 deletions(-)
diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
index 9e2c1ecaaf4f..37f80e368551 100644
--- a/drivers/vfio/device_cdev.c
+++ b/drivers/vfio/device_cdev.c
@@ -3,6 +3,7 @@
* Copyright (c) 2023 Intel Corporation.
*/
#include <linux/vfio.h>
+#include <linux/iommufd.h>
#include "vfio.h"
@@ -45,6 +46,151 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep)
return ret;
}
+static void vfio_device_get_kvm_safe(struct vfio_device_file *df)
+{
+ spin_lock(&df->kvm_ref_lock);
+ if (!df->kvm)
+ goto unlock;
+
+ _vfio_device_get_kvm_safe(df->device, df->kvm);
+
+unlock:
+ spin_unlock(&df->kvm_ref_lock);
+}
+
+void vfio_device_cdev_close(struct vfio_device_file *df)
+{
+ struct vfio_device *device = df->device;
+
+ mutex_lock(&device->dev_set->lock);
+ /*
+ * As df->access_granted writer is under dev_set->lock as well,
+ * so this read no need to use smp_load_acquire() to pair with
+ * smp_store_release() in the caller of vfio_device_open().
+ */
+ if (!df->access_granted) {
+ mutex_unlock(&device->dev_set->lock);
+ return;
+ }
+ vfio_device_close(df);
+ vfio_device_put_kvm(device);
+ if (df->iommufd)
+ iommufd_ctx_put(df->iommufd);
+ mutex_unlock(&device->dev_set->lock);
+ vfio_device_unblock_group(device);
+}
+
+static struct iommufd_ctx *vfio_get_iommufd_from_fd(int fd)
+{
+ struct fd f;
+ struct iommufd_ctx *iommufd;
+
+ f = fdget(fd);
+ if (!f.file)
+ return ERR_PTR(-EBADF);
+
+ iommufd = iommufd_ctx_from_file(f.file);
+
+ fdput(f);
+ return iommufd;
+}
+
+long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
+ unsigned long arg)
+{
+ struct vfio_device *device = df->device;
+ struct vfio_device_bind_iommufd bind;
+ struct iommufd_ctx *iommufd = NULL;
+ unsigned long minsz;
+ int ret;
+
+ minsz = offsetofend(struct vfio_device_bind_iommufd, out_devid);
+
+ if (copy_from_user(&bind, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (bind.argsz < minsz || bind.flags)
+ return -EINVAL;
+
+ if (!device->ops->bind_iommufd)
+ return -ENODEV;
+
+ ret = vfio_device_block_group(device);
+ if (ret)
+ return ret;
+
+ mutex_lock(&device->dev_set->lock);
+ /*
+ * If already been bound to an iommufd, or already set noiommu
+ * then fail it.
+ */
+ if (df->iommufd || df->noiommu) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ /* iommufd < 0 means noiommu mode */
+ if (bind.iommufd < 0) {
+ if (!capable(CAP_SYS_RAWIO)) {
+ ret = -EPERM;
+ goto out_unlock;
+ }
+ df->noiommu = true;
+ } else {
+ iommufd = vfio_get_iommufd_from_fd(bind.iommufd);
+ if (IS_ERR(iommufd)) {
+ ret = PTR_ERR(iommufd);
+ goto out_unlock;
+ }
+ }
+
+ /*
+ * Before the device open, get the KVM pointer currently
+ * associated with the device file (if there is) and obtain
+ * a reference. This reference is held until device closed.
+ * Save the pointer in the device for use by drivers.
+ */
+ vfio_device_get_kvm_safe(df);
+
+ df->iommufd = iommufd;
+ ret = vfio_device_open(df, &bind.out_devid, NULL);
This is unrelated to this patch but reminded me - while debugging QEMU,
vfio_assert_device_open() kept firing as I was killing QEMU (which in
turn made the kernel close all fds), device->open_count==0 as QEMU was
dying before calling ioctl(VFIO_DEVICE_BIND_IOMMUFD) which would call
this vfio_device_open() just above. Has this been reported/fixed, just
curious?
--
Alexey
