xenclient: implement page claims for early low memory warning

xencall/src/lib.rs

@@ -10,7 +10,7 @@ use crate::sys::{
     XEN_DOMCTL_GETDOMAININFO, XEN_DOMCTL_GETPAGEFRAMEINFO3, XEN_DOMCTL_GETVCPUCONTEXT,
     XEN_DOMCTL_HYPERCALL_INIT, XEN_DOMCTL_INTERFACE_VERSION, XEN_DOMCTL_MAX_MEM,
     XEN_DOMCTL_MAX_VCPUS, XEN_DOMCTL_PAUSEDOMAIN, XEN_DOMCTL_SETVCPUCONTEXT,
-    XEN_DOMCTL_SET_ADDRESS_SIZE, XEN_DOMCTL_UNPAUSEDOMAIN, XEN_MEM_MEMORY_MAP,
+    XEN_DOMCTL_SET_ADDRESS_SIZE, XEN_DOMCTL_UNPAUSEDOMAIN, XEN_MEM_CLAIM_PAGES, XEN_MEM_MEMORY_MAP,
     XEN_MEM_POPULATE_PHYSMAP,
 };
 use libc::{c_int, mmap, usleep, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE};
@@ -644,6 +644,28 @@ impl XenCall {
         Ok(extents)
     }
 
+    pub fn claim_pages(&self, domid: u32, pages: u64) -> Result<(), XenCallError> {
+        trace!(
+            "memory fd={} claim_pages domid={} pages={}",
+            self.handle.as_raw_fd(),
+            domid,
+            pages
+        );
+        let mut reservation = MemoryReservation {
+            extent_start: 0,
+            nr_extents: pages,
+            extent_order: 0,
+            mem_flags: 0,
+            domid: domid as u16,
+        };
+        self.hypercall2(
+            HYPERVISOR_MEMORY_OP,
+            XEN_MEM_CLAIM_PAGES as c_ulong,
+            addr_of_mut!(reservation) as c_ulong,
+        )?;
+        Ok(())
+    }
+
     pub fn mmuext(
         &self,
         domid: u32,

xencall/src/sys.rs

@@ -365,6 +365,7 @@ pub struct MultiCallEntry {
 
 pub const XEN_MEM_POPULATE_PHYSMAP: u32 = 6;
 pub const XEN_MEM_MEMORY_MAP: u32 = 9;
+pub const XEN_MEM_CLAIM_PAGES: u32 = 24;
 
 #[repr(C)]
 #[derive(Copy, Clone, Debug)]