refactor: do not redefine x86 constant in test_vsock_bof

This test is all about testing what happens when a vsock driver places
virtio buffers close to / around the MMIO gap on x86_64 systems. Since
this test thus doesn't really serve a purpose on aarch64, we can just
cfg(target_arch = "x86_64") it, and reuse the constants from
arch::x86_64 instead of redefining them again.

fwiw, I have no idea what "bof" means. I'm also confused by this test
passing on ARM in the first place, given that some of the comments
indicate to me that it should fail if the buffers overlap the mmio gap
(which doesn't exist on arm, so nothing should fail?).

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/vmm/src/arch/x86_64/mod.rs

@@ -67,7 +67,8 @@ pub enum ConfigurationError {
     StartInfoSetup,
 }
 
-const FIRST_ADDR_PAST_32BITS: u64 = 1 << 32;
+/// First address that cannot be addressed using 32 bit anymore.
+pub const FIRST_ADDR_PAST_32BITS: u64 = 1 << 32;
 
 /// Size of MMIO gap at top of 32-bit address space.
 pub const MEM_32BIT_GAP_SIZE: u64 = 768 << 20;

src/vmm/src/devices/virtio/vsock/event_handler.rs

@@ -223,10 +223,7 @@ mod tests {
 
     use super::super::*;
     use super::*;
-    use crate::devices::virtio::vsock::packet::VSOCK_PKT_HDR_SIZE;
     use crate::devices::virtio::vsock::test_utils::{EventHandlerContext, TestContext};
-    use crate::test_utils::multi_region_mem;
-    use crate::vstate::memory::Bytes;
 
     #[test]
     fn test_txq_event() {
@@ -427,8 +424,9 @@ mod tests {
     // function for testing error cases, so the asserts always expect is_err() to be true. When
     // desc_idx = 0 we are altering the header (first descriptor in the chain), and when
     // desc_idx = 1 we are altering the packet buffer.
+    #[cfg(target_arch = "x86_64")]
     fn vsock_bof_helper(test_ctx: &mut TestContext, desc_idx: usize, addr: u64, len: u32) {
-        use crate::vstate::memory::GuestAddress;
+        use crate::vstate::memory::{Bytes, GuestAddress};
 
         assert!(desc_idx <= 1);
 
@@ -472,19 +470,22 @@ mod tests {
     }
 
     #[test]
+    #[cfg(target_arch = "x86_64")]
+    #[allow(clippy::cast_possible_truncation)] /* casting of constants we know fit into u32 */
     fn test_vsock_bof() {
+        use crate::arch::MMIO_MEM_START;
+        use crate::arch::x86_64::{FIRST_ADDR_PAST_32BITS, MEM_32BIT_GAP_SIZE};
+        use crate::devices::virtio::vsock::packet::VSOCK_PKT_HDR_SIZE;
+        use crate::test_utils::multi_region_mem;
         use crate::vstate::memory::GuestAddress;
 
-        const GAP_SIZE: u32 = 768 << 20;
-        const FIRST_AFTER_GAP: usize = 1 << 32;
-        const GAP_START_ADDR: usize = FIRST_AFTER_GAP - GAP_SIZE as usize;
         const MIB: usize = 1 << 20;
 
         let mut test_ctx = TestContext::new();
         test_ctx.mem = multi_region_mem(&[
             (GuestAddress(0), 8 * MIB),
-            (GuestAddress((GAP_START_ADDR - MIB) as u64), MIB),
-            (GuestAddress(FIRST_AFTER_GAP as u64), MIB),
+            (GuestAddress(MMIO_MEM_START - MIB as u64), MIB),
+            (GuestAddress(FIRST_ADDR_PAST_32BITS), MIB),
         ]);
 
         // The default configured descriptor chains are valid.
@@ -506,20 +507,25 @@ mod tests {
         }
 
         // Let's check what happens when the header descriptor is right before the gap.
-        vsock_bof_helper(
-            &mut test_ctx,
-            0,
-            GAP_START_ADDR as u64 - 1,
-            VSOCK_PKT_HDR_SIZE,
-        );
+        vsock_bof_helper(&mut test_ctx, 0, MMIO_MEM_START - 1, VSOCK_PKT_HDR_SIZE);
 
         // Let's check what happens when the buffer descriptor crosses into the gap, but does
         // not go past its right edge.
-        vsock_bof_helper(&mut test_ctx, 1, GAP_START_ADDR as u64 - 4, GAP_SIZE + 4);
+        vsock_bof_helper(
+            &mut test_ctx,
+            1,
+            MMIO_MEM_START - 4,
+            MEM_32BIT_GAP_SIZE as u32 + 4,
+        );
 
         // Let's modify the buffer descriptor addr and len such that it crosses over the MMIO gap,
         // and check we cannot assemble the VsockPkts.
-        vsock_bof_helper(&mut test_ctx, 1, GAP_START_ADDR as u64 - 4, GAP_SIZE + 100);
+        vsock_bof_helper(
+            &mut test_ctx,
+            1,
+            MMIO_MEM_START - 4,
+            MEM_32BIT_GAP_SIZE as u32 + 100,
+        );
     }
 
     #[test]