Accept externally-opened /dev/iommu File

iommufd-ioctls/CHANGELOG.md

@@ -3,6 +3,10 @@
 ## Changed
 
 ## Added
+- [[9]](https://github.com/cloud-hypervisor/iommufd/pull/9) Add `Iommufd::destroy_iommu_object` to release iommufd
+  objects explicitly.
+- [[9]](https://github.com/cloud-hypervisor/iommufd/pull/9) Add `Iommufd::new_from_fd` to construct a `Iommufd` from
+  a pre-opened iommufd file.
 
 ## Fixed
 

iommufd-ioctls/src/iommufd_ioctls.rs

@@ -26,6 +26,20 @@ impl IommuFd {
         Ok(IommuFd { iommufd })
     }
 
+    /// New from an already-opened `/dev/iommu` file. Caller transfers
+    /// ownership; closing the fd is now `IommuFd`'s responsibility.
+    pub fn new_from_fd(file: File) -> Self {
+        IommuFd { iommufd: file }
+    }
+
+    pub fn destroy_iommu_object(&self, id: u32) -> Result<()> {
+        let destroy_data = iommu_destroy {
+            size: std::mem::size_of::<iommu_destroy>() as u32,
+            id,
+        };
+        iommufd_syscall::destroy_iommu_object(self, &destroy_data)
+    }
+
     pub fn alloc_iommu_ioas(&self, alloc_data: &mut iommu_ioas_alloc) -> Result<()> {
         iommufd_syscall::alloc_iommu_ioas(self, alloc_data)
     }
@@ -44,6 +58,7 @@ impl AsRawFd for IommuFd {
     }
 }
 
+ioctl_io_nr!(IOMMU_DESTROY, IOMMUFD_TYPE as u32, IOMMUFD_CMD_DESTROY);
 ioctl_io_nr!(
     IOMMU_IOAS_ALLOC,
     IOMMUFD_TYPE as u32,
@@ -64,6 +79,23 @@ pub(crate) mod iommufd_syscall {
     use super::*;
     use vmm_sys_util::ioctl::{ioctl_with_mut_ref, ioctl_with_ref};
 
+    pub(crate) fn destroy_iommu_object(
+        iommufd: &IommuFd,
+        destroy_data: &iommu_destroy,
+    ) -> Result<()> {
+        // SAFETY:
+        // 1. The file descriptor provided by 'iommufd' is valid and open.
+        // 2. The 'destroy_data' points to initialized memory with expected data structure,
+        // and remains valid for the duration of sysca
+        // 3. The return value is checked.
+        let ret = unsafe { ioctl_with_ref(iommufd, IOMMU_DESTROY(), destroy_data) };
+        if ret < 0 {
+            Err(IommufdError::IommuDestroy(SysError::last()))
+        } else {
+            Ok(())
+        }
+    }
+
     pub(crate) fn alloc_iommu_ioas(
         iommufd: &IommuFd,
         alloc_data: &mut iommu_ioas_alloc,
@@ -115,6 +147,7 @@ mod tests {
 
     #[test]
     fn test_iommufd_ioctl_code() {
+        assert_eq!(IOMMU_DESTROY(), 15232);
         assert_eq!(IOMMU_IOAS_ALLOC(), 15233);
         assert_eq!(IOMMU_IOAS_MAP(), 15237);
         assert_eq!(IOMMU_IOAS_UNMAP(), 15238);

iommufd-ioctls/src/lib.rs

@@ -18,6 +18,8 @@ pub use iommufd_ioctls::*;
 pub enum IommufdError {
     #[error("failed to open /dev/iommufd: {0}")]
     OpenIommufd(#[source] io::Error),
+    #[error("failed to destroy iommufd object: {0}")]
+    IommuDestroy(#[source] SysError),
     #[error("failed to allocate IOAS: {0}")]
     IommuIoasAlloc(#[source] SysError),
     #[error("failed to map an IOVA range to the IOAS: {0}")]