actually allocate max memory

xencall/src/memory.rs

@@ -3,7 +3,7 @@ use crate::{XenCall, XenCallError};
 
 use std::ffi::c_ulong;
 
-use std::ptr::addr_of;
+use std::ptr::addr_of_mut;
 
 pub struct MemoryControl<'a> {
     call: &'a XenCall,
@@ -22,19 +22,28 @@ impl MemoryControl<'_> {
         mem_flags: u32,
         extent_starts: &[u64],
     ) -> Result<Vec<u64>, XenCallError> {
-        let extent_starts = extent_starts.to_vec();
-        let reservation = MemoryReservation {
-            extent_start: addr_of!(extent_starts) as c_ulong,
+        let mut extent_starts = extent_starts.to_vec();
+        let mut reservation = MemoryReservation {
+            extent_start: extent_starts.as_mut_ptr() as c_ulong,
             nr_extents,
             extent_order,
             mem_flags,
             domid: domid as u16,
         };
-        self.call.hypercall2(
+        let code = self.call.hypercall2(
             HYPERVISOR_MEMORY_OP,
             XEN_MEM_POPULATE_PHYSMAP as c_ulong,
-            addr_of!(reservation) as c_ulong,
+            addr_of_mut!(reservation) as c_ulong,
         )?;
-        Ok(extent_starts)
+
+        if code < 0 {
+            return Err(XenCallError::new("failed to populate physmap"));
+        }
+
+        if code as usize > extent_starts.len() {
+            return Err(XenCallError::new("failed to populate physmap"));
+        }
+
+        Ok(extent_starts[0..code as usize].to_vec())
     }
 }