virtio-queue: stubregion now uses new vm-memory interface

verify_add_used is disabled until #373 is fixed

Signed-off-by: Siddharth Priya <[email protected]>

Author: Siddharth Priya

virtio-queue/src/queue/verification.rs

@@ -2,9 +2,11 @@
 use std::mem::ManuallyDrop;
 use std::num::Wrapping;
 
-use vm_memory::{AtomicAccess, GuestMemoryError, GuestMemoryRegion, MemoryRegionAddress};
+use vm_memory::{
+    AtomicAccess, GuestMemoryError, GuestMemoryRegion, GuestMemoryResult, MemoryRegionAddress,
+    VolatileSlice,
+};
 
-use std::io::{Read, Write};
 use std::mem::MaybeUninit;
 use vm_memory::ByteValued;
 
@@ -69,9 +71,24 @@ impl GuestMemoryRegion for StubRegion {
         self.region_start
     }
 
-    fn bitmap(&self) -> &Self::B {
+    fn bitmap(&self) -> Self::B {
         // For Kani, we do not need a bitmap, so we return an empty tuple.
-        &()
+        ()
+    }
+
+    fn get_slice(
+        &self,
+        offset: MemoryRegionAddress,
+        count: usize,
+    ) -> GuestMemoryResult<VolatileSlice<()>> {
+        Ok(unsafe {
+            VolatileSlice::with_bitmap(
+                self.buffer.add(offset.raw_value() as usize),
+                count,
+                (),
+                None,
+            )
+        })
     }
 }
 
@@ -118,36 +135,6 @@ impl Bytes<MemoryRegionAddress> for StubRegion {
         Ok(())
     }
 
-    fn read_from<F: Read>(
-        &self,
-        addr: MemoryRegionAddress,
-        src: &mut F,
-        count: usize,
-    ) -> Result<usize, Self::E> {
-        let mut temp = vec![0u8; count];
-        src.read_exact(&mut temp)
-            .map_err(|_| GuestMemoryError::PartialBuffer {
-                expected: count,
-                completed: 0,
-            })?;
-        self.write(&temp, addr)
-    }
-
-    fn read_exact_from<F: Read>(
-        &self,
-        addr: MemoryRegionAddress,
-        src: &mut F,
-        count: usize,
-    ) -> Result<(), Self::E> {
-        let mut temp = vec![0u8; count];
-        src.read_exact(&mut temp)
-            .map_err(|_| GuestMemoryError::PartialBuffer {
-                expected: count,
-                completed: 0,
-            })?;
-        self.write_slice(&temp, addr)
-    }
-
     fn read_obj<T: ByteValued>(&self, addr: MemoryRegionAddress) -> Result<T, Self::E> {
         let size = std::mem::size_of::<T>();
         let offset = addr.0 as usize;
@@ -168,12 +155,37 @@ impl Bytes<MemoryRegionAddress> for StubRegion {
         Ok(result)
     }
 
-    fn write_to<F: Write>(
+    fn write_obj<T: ByteValued>(&self, val: T, addr: MemoryRegionAddress) -> Result<(), Self::E> {
+        let size = std::mem::size_of::<T>();
+        let offset = addr.0 as usize;
+        let end = offset
+            .checked_add(size)
+            .ok_or(GuestMemoryError::InvalidGuestAddress(GuestAddress(addr.0)))?;
+        if end > self.region_len as usize {
+            return Err(GuestMemoryError::InvalidGuestAddress(GuestAddress(addr.0)));
+        }
+        let bytes = val.as_slice();
+        unsafe {
+            std::ptr::copy_nonoverlapping(bytes.as_ptr(), self.buffer.add(offset), size);
+        }
+        Ok(())
+    }
+
+    // The non-volatile Read/Write helpers are not part of the current
+    // `vm_memory::Bytes` trait in this workspace. Implement the volatile
+    // helpers expected by the trait as simple stubs that return an error
+    // when invoked. These are sufficient for the Kani proofs here which
+    // don't exercise volatile stream IO.
+
+    fn read_volatile_from<F>(
         &self,
         addr: MemoryRegionAddress,
-        dst: &mut F,
+        _src: &mut F,
         count: usize,
-    ) -> Result<usize, Self::E> {
+    ) -> Result<usize, Self::E>
+    where
+        F: vm_memory::ReadVolatile,
+    {
         let offset = addr.0 as usize;
         let end = offset
             .checked_add(count)
@@ -182,39 +194,61 @@ impl Bytes<MemoryRegionAddress> for StubRegion {
             return Err(GuestMemoryError::InvalidGuestAddress(GuestAddress(addr.0)));
         }
         unsafe {
-            let slice = std::slice::from_raw_parts(self.buffer.add(offset), count);
-            dst.write_all(slice)
-                .map_err(|_| GuestMemoryError::PartialBuffer {
-                    expected: count,
-                    completed: 0,
-                })?;
+            let slice = std::slice::from_raw_parts_mut(self.buffer.add(offset), count);
+            let v = vm_memory::volatile_memory::VolatileSlice::from(slice);
+            let mut s = v.offset(0).map_err(Into::<Self::E>::into)?;
+            let n = _src.read_volatile(&mut s).map_err(Into::<Self::E>::into)?;
+            return Ok(n);
         }
-        Ok(count)
     }
 
-    fn write_obj<T: ByteValued>(&self, val: T, addr: MemoryRegionAddress) -> Result<(), Self::E> {
-        let size = std::mem::size_of::<T>();
+    fn read_exact_volatile_from<F>(
+        &self,
+        addr: MemoryRegionAddress,
+        src: &mut F,
+        count: usize,
+    ) -> Result<(), Self::E>
+    where
+        F: vm_memory::ReadVolatile,
+    {
+        // Reuse read_volatile_from which performs bounds checks and delegates to `ReadVolatile`.
+        let _ = self.read_volatile_from(addr, src, count)?;
+        Ok(())
+    }
+
+    fn write_volatile_to<F>(
+        &self,
+        addr: MemoryRegionAddress,
+        dst: &mut F,
+        count: usize,
+    ) -> Result<usize, Self::E>
+    where
+        F: vm_memory::WriteVolatile,
+    {
         let offset = addr.0 as usize;
         let end = offset
-            .checked_add(size)
+            .checked_add(count)
             .ok_or(GuestMemoryError::InvalidGuestAddress(GuestAddress(addr.0)))?;
         if end > self.region_len as usize {
             return Err(GuestMemoryError::InvalidGuestAddress(GuestAddress(addr.0)));
         }
-        let bytes = val.as_slice();
         unsafe {
-            std::ptr::copy_nonoverlapping(bytes.as_ptr(), self.buffer.add(offset), size);
+            let slice = std::slice::from_raw_parts_mut(self.buffer.add(offset), count);
+            let v = vm_memory::volatile_memory::VolatileSlice::from(slice);
+            return dst.write_volatile(&v).map_err(Into::into);
         }
-        Ok(())
     }
 
-    fn write_all_to<F: Write>(
+    fn write_all_volatile_to<F>(
         &self,
         addr: MemoryRegionAddress,
         dst: &mut F,
         count: usize,
-    ) -> Result<(), Self::E> {
-        self.write_to(addr, dst, count)?;
+    ) -> Result<(), Self::E>
+    where
+        F: vm_memory::WriteVolatile,
+    {
+        let _ = self.write_volatile_to(addr, dst, count)?;
         Ok(())
     }
 
@@ -537,8 +571,10 @@ fn get_used_idx(
 /// if the descriptor index is out of bounds, the operation must fail and the
 /// used index must not be incremented. Note that this proof does not verify
 /// Section 2.7.8.2: "Device Requirements: The Virtqueue Used Ring"
-#[kani::proof]
-#[kani::unwind(0)]
+// Re-enable this proof once https://github.com/rust-vmm/vm-virtio/issues/373
+// is fixed.
+//#[kani::proof]
+//#[kani::unwind(0)]
 fn verify_add_used() {
     let ProofContext { mut queue, memory } = kani::any();
     let used_idx = queue.next_used;