Add packed descriptor

Add the packed descriptor for support packed vring.

Signed-off-by: Wenyu Huang <[email protected]>

Author: uran0sH

virtio-queue/src/desc/mod.rs

@@ -2,6 +2,7 @@
 
 use vm_memory::{ByteValued, Le16, Le32, Le64};
 
+pub mod packed;
 pub mod split;
 
 /// A virtio descriptor's layout constraints with C representation.
@@ -27,17 +28,34 @@ impl From<split::Descriptor> for Descriptor {
     }
 }
 
+impl From<packed::Descriptor> for Descriptor {
+    fn from(desc: packed::Descriptor) -> Self {
+        Descriptor(
+            Le64::from(desc.addr().0),
+            Le32::from(desc.len()),
+            Le16::from(desc.id()),
+            Le16::from(desc.flags()),
+        )
+    }
+}
+
 impl From<Descriptor> for split::Descriptor {
     fn from(desc: Descriptor) -> split::Descriptor {
         split::Descriptor::new(desc.0.into(), desc.1.into(), desc.2.into(), desc.3.into())
     }
 }
 
+impl From<Descriptor> for packed::Descriptor {
+    fn from(desc: Descriptor) -> packed::Descriptor {
+        packed::Descriptor::new(desc.0.into(), desc.1.into(), desc.2.into(), desc.3.into())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use vm_memory::{Le16, Le32, Le64};
 
-    use super::{split, Descriptor};
+    use super::{packed, split, Descriptor};
 
     #[test]
     fn test_desc_from_split() {
@@ -58,4 +76,24 @@ mod tests {
         assert_eq!(split_desc.flags(), desc.2);
         assert_eq!(split_desc.next(), desc.3);
     }
+
+    #[test]
+    fn test_desc_from_packed() {
+        let packed_desc = packed::Descriptor::new(1, 2, 3, 4);
+        let desc = Descriptor::from(packed_desc);
+        assert_eq!(packed_desc.addr().0, desc.0);
+        assert_eq!(packed_desc.len(), desc.1);
+        assert_eq!(packed_desc.id(), desc.2);
+        assert_eq!(packed_desc.flags(), desc.3);
+    }
+
+    #[test]
+    fn test_packed_from_desc() {
+        let desc = Descriptor(Le64::from(1), Le32::from(2), Le16::from(3), Le16::from(4));
+        let packed_desc = packed::Descriptor::from(desc);
+        assert_eq!(packed_desc.addr().0, desc.0);
+        assert_eq!(packed_desc.len(), desc.1);
+        assert_eq!(packed_desc.id(), desc.2);
+        assert_eq!(packed_desc.flags(), desc.3);
+    }
 }

virtio-queue/src/desc/packed.rs

@@ -0,0 +1,203 @@
+//! packed descriptor
+use virtio_bindings::bindings::virtio_ring::{
+    VRING_DESC_F_INDIRECT, VRING_DESC_F_NEXT, VRING_DESC_F_WRITE,
+};
+use vm_memory::{ByteValued, GuestAddress, Le16, Le32, Le64};
+
+/// A virtio packed descriptor constraints with C representation.
+#[repr(C)]
+#[derive(Default, Clone, Copy, Debug)]
+pub struct Descriptor {
+    /// Guest physical address of device specific data.
+    addr: Le64,
+    /// Length of device specific data.
+    len: Le32,
+    /// Index of descriptor in the descriptor table.
+    id: Le16,
+    /// Includes next, write, and indirect bits.
+    flags: Le16,
+}
+
+#[allow(clippy::len_without_is_empty)]
+impl Descriptor {
+    /// Return the guest physical address of the descriptor buffer.
+    pub fn addr(&self) -> GuestAddress {
+        GuestAddress(self.addr.into())
+    }
+
+    /// Return the length of the descriptor buffer.
+    pub fn len(&self) -> u32 {
+        self.len.into()
+    }
+
+    /// Return the flags for this descriptor, including next, write and indirect bits.
+    pub fn flags(&self) -> u16 {
+        self.flags.into()
+    }
+
+    /// Return the index of the descriptor in the descriptor table.
+    pub fn id(&self) -> u16 {
+        self.id.into()
+    }
+
+    /// Check whether this descriptor refers to a buffer containing an indirect descriptor table.
+    pub fn refers_to_indirect_table(&self) -> bool {
+        self.flags() & VRING_DESC_F_INDIRECT as u16 != 0
+    }
+
+    /// Check whether the `VIRTQ_DESC_F_NEXT` is set for the descriptor.
+    pub fn has_next(&self) -> bool {
+        self.flags() & VRING_DESC_F_NEXT as u16 != 0
+    }
+
+    /// Check if the driver designated this as a write only descriptor.
+    ///
+    /// If this is false, this descriptor is read only.
+    /// Write only means the the emulated device can write and the driver can read.
+    pub fn is_write_only(&self) -> bool {
+        self.flags() & VRING_DESC_F_WRITE as u16 != 0
+    }
+}
+
+impl Descriptor {
+    /// Create a new descriptor.
+    ///
+    /// # Arguments
+    /// * `addr` - the guest physical address of the descriptor buffer.
+    /// * `len` - the length of the descriptor buffer.
+    /// * `flags` - the `flags` for the descriptor.
+    /// * `next` - the `next` field of the descriptor.
+    pub fn new(addr: u64, len: u32, id: u16, flags: u16) -> Self {
+        Descriptor {
+            addr: addr.into(),
+            len: len.into(),
+            id: id.into(),
+            flags: flags.into(),
+        }
+    }
+
+    /// Set the guest physical address of the descriptor buffer.
+    pub fn set_addr(&mut self, addr: u64) {
+        self.addr = addr.into();
+    }
+
+    /// Set the length of the descriptor buffer.
+    pub fn set_len(&mut self, len: u32) {
+        self.len = len.into();
+    }
+
+    /// Set the flags for this descriptor.
+    pub fn set_flags(&mut self, flags: u16) {
+        self.flags = flags.into();
+    }
+
+    /// Set the value stored in the `next` field of the descriptor.
+    pub fn set_id(&mut self, id: u16) {
+        self.id = id.into();
+    }
+}
+
+// SAFETY: This is safe because `Descriptor` contains only wrappers over POD types and
+// all accesses through safe `vm-memory` API will validate any garbage that could be
+// included in there.
+unsafe impl ByteValued for Descriptor {}
+
+/// A packed descriptor event constraints with C representation.
+#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+pub struct PackedDescEvent {
+    off_wrap: Le16,
+    flags: Le16,
+}
+
+impl PackedDescEvent {
+    /// Create a new `VirtqUsedElem` instance.
+    ///
+    /// # Arguments
+    /// * `id` - the index of the used descriptor chain.
+    /// * `len` - the total length of the descriptor chain which was used (written to).
+    #[allow(unused)]
+    pub(crate) fn new(off_wrap: u16, flags: u16) -> Self {
+        PackedDescEvent {
+            off_wrap: off_wrap.into(),
+            flags: flags.into(),
+        }
+    }
+}
+
+// SAFETY: This is safe because `PackedDescEvent` contains only wrappers over POD types and
+// all accesses through safe `vm-memory` API will validate any garbage that could be
+// included in there.
+unsafe impl ByteValued for PackedDescEvent {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use memoffset::offset_of;
+    use std::mem::{align_of, size_of};
+
+    #[test]
+    fn test_descriptor_offset() {
+        assert_eq!(size_of::<Descriptor>(), 16);
+        assert_eq!(offset_of!(Descriptor, addr), 0);
+        assert_eq!(offset_of!(Descriptor, len), 8);
+        assert_eq!(offset_of!(Descriptor, id), 12);
+        assert_eq!(offset_of!(Descriptor, flags), 14);
+        assert!(align_of::<Descriptor>() <= 16);
+    }
+
+    #[test]
+    fn test_descriptor_getter_setter() {
+        let mut desc = Descriptor::new(0, 0, 0, 0);
+
+        desc.set_addr(0x1000);
+        assert_eq!(desc.addr(), GuestAddress(0x1000));
+        desc.set_len(0x2000);
+        assert_eq!(desc.len(), 0x2000);
+        desc.set_flags(VRING_DESC_F_NEXT as u16);
+        assert_eq!(desc.flags(), VRING_DESC_F_NEXT as u16);
+        assert!(desc.has_next());
+        assert!(!desc.is_write_only());
+        assert!(!desc.refers_to_indirect_table());
+        desc.set_flags(VRING_DESC_F_WRITE as u16);
+        assert_eq!(desc.flags(), VRING_DESC_F_WRITE as u16);
+        assert!(!desc.has_next());
+        assert!(desc.is_write_only());
+        assert!(!desc.refers_to_indirect_table());
+        desc.set_flags(VRING_DESC_F_INDIRECT as u16);
+        assert_eq!(desc.flags(), VRING_DESC_F_INDIRECT as u16);
+        assert!(!desc.is_write_only());
+        assert!(desc.refers_to_indirect_table());
+        desc.set_id(1);
+        assert_eq!(desc.id(), 1);
+    }
+
+    #[test]
+    fn test_descriptor_copy() {
+        let e1 = Descriptor::new(1, 2, 0, 3);
+        let mut e2 = Descriptor::default();
+
+        e2.as_mut_slice().copy_from_slice(e1.as_slice());
+        assert_eq!(e1.addr(), e2.addr());
+        assert_eq!(e1.len(), e2.len());
+        assert_eq!(e1.id(), e2.id());
+        assert_eq!(e1.flags(), e2.flags());
+    }
+
+    #[test]
+    fn test_packed_desc_event_offset() {
+        assert_eq!(offset_of!(PackedDescEvent, off_wrap), 0);
+        assert_eq!(offset_of!(PackedDescEvent, flags), 2);
+        assert_eq!(size_of::<PackedDescEvent>(), 4);
+    }
+
+    #[test]
+    fn test_packed_desc_event_copy() {
+        let e1 = PackedDescEvent::new(1, 2);
+        let mut e2 = PackedDescEvent::new(0, 0);
+
+        e2.as_mut_slice().copy_from_slice(e1.as_slice());
+        assert_eq!(e1.off_wrap, e2.off_wrap);
+        assert_eq!(e1.flags, e2.flags);
+    }
+}