[Xen-devel] [PATCH] xenpaging: handle XENMEM_decrease_reservation

[Olaf Hering <olaf@xxxxxxxxx>]

Handle paged-out pages for XENMEM_decrease_reservation memory op.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

---
 tools/libxc/xc_domain.c |   38 ++++++++++++++++++++++++++------------
 xen/common/memory.c     |    4 ++++
 2 files changed, 30 insertions(+), 12 deletions(-)

--- xen-unstable.hg-4.1.22155.orig/tools/libxc/xc_domain.c
+++ xen-unstable.hg-4.1.22155/tools/libxc/xc_domain.c
@@ -620,15 +620,15 @@ int xc_domain_memory_decrease_reservatio
                                           xen_pfn_t *extent_start)
 {
     int err;
+    unsigned long delay = 0;
+    unsigned long start = 0;
+    unsigned long count= nr_extents;
     struct xen_memory_reservation reservation = {
-        .nr_extents   = nr_extents,
         .extent_order = extent_order,
         .mem_flags    = 0,
         .domid        = domid
     };
 
-    set_xen_guest_handle(reservation.extent_start, extent_start);
-
     if ( extent_start == NULL )
     {
         DPRINTF("decrease_reservation extent_start is NULL!\n");
@@ -636,16 +636,30 @@ int xc_domain_memory_decrease_reservatio
         return -1;
     }
 
-    err = xc_memory_op(xch, XENMEM_decrease_reservation, &reservation);
-    if ( err == nr_extents )
-        return 0;
+    while (1) {
+        set_xen_guest_handle(reservation.extent_start, extent_start + start);
+        reservation.nr_extents = count;
 
-    if ( err >= 0 )
-    {
-        DPRINTF("Failed deallocation for dom %d: %ld extents of order %d\n",
-                domid, nr_extents, extent_order);
-        errno = EINVAL;
-        err = -1;
+        err = xc_memory_op(xch, XENMEM_decrease_reservation, &reservation);
+        if ( err == count )
+        {
+            err = 0;
+            break;
+        }
+
+        if ( err > count || err <= 0 || delay > 1000 * 1000)
+        {
+            DPRINTF("Failed deallocation for dom %d: %ld extents of order %d: 
0x%x\n",
+                    domid, nr_extents, extent_order, err);
+            errno = EINVAL;
+            err = -1;
+            break;
+        }
+
+        start += err;
+        count -= err;
+        usleep(delay);
+        delay += 666; /* 1500 iterations, 12 seconds */
     }
 
     return err;
--- xen-unstable.hg-4.1.22155.orig/xen/common/memory.c
+++ xen-unstable.hg-4.1.22155/xen/common/memory.c
@@ -162,6 +162,10 @@ int guest_remove_page(struct domain *d,
 
 #ifdef CONFIG_X86
     mfn = mfn_x(gfn_to_mfn(p2m_get_hostp2m(d), gmfn, &p2mt)); 
+    if ( p2m_is_paged(p2mt) )
+        p2m_mem_paging_populate(p2m_get_hostp2m(d), gmfn);
+    if ( p2m_is_paging(p2mt) )
+        return -ENOENT;
 #else
     mfn = gmfn_to_mfn(d, gmfn);
 #endif

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