Xen devel - May 2009 - [PATCH 5/6] Extend XENMEM_exchange to support exchange memory for foreign domain

Currently XENMEM_exchange only support exchange memory for current domain, This
patch extend it to foreign domain once the target domain is in suspended state.

Signed-off-by: Jiang, Yunhogn <yunhong.jiang@intel.com>Now comes changes
to hypervisor

diff -r 1fe86c971a36 xen/common/memory.c
--- a/xen/common/memory.c	Wed May 27 03:22:43 2009 +0800
+++ b/xen/common/memory.c	Wed May 27 03:42:29 2009 +0800
@@ -23,6 +23,7 @@
 #include <asm/hardirq.h>
 #include <xen/numa.h>
 #include <public/memory.h>
+#include <public/sched.h>
 #include <xsm/xsm.h>
 
 struct memop_args {
@@ -225,7 +226,7 @@ static long memory_exchange(XEN_GUEST_HA
     unsigned long i, j, k;
     unsigned int  node, memflags = 0;
     long          rc = 0;
-    struct domain *d;
+    struct domain *d = NULL;
     struct page_info *page;
 
     if ( copy_from_guest(&exch, arg, 1) )
@@ -266,15 +267,28 @@ static long memory_exchange(XEN_GUEST_HA
     }
 
     /*
-     * Only support exchange on calling domain right now. Otherwise there are
-     * tricky corner cases to consider (e.g., dying domain).
+     * Mostly support exchange on calling domain right now. Otherwise the
+     * target domain should be in suspended state
      */
     if ( unlikely(exch.in.domid != DOMID_SELF) )
     {
-        rc = IS_PRIV(current->domain) ? -EINVAL : -EPERM;
-        goto fail_early;
-    }
-    d = current->domain;
+        d = rcu_lock_domain_by_id(exch.in.domid);
+        if (!d)
+        {
+            rc = -EINVAL;
+            goto fail_early;
+        }
+        spin_lock(&d->shutdown_lock);
+
+        if ( (!d->is_shut_down) || (d->shutdown_code != SHUTDOWN_suspend)
)
+        {
+            rc = -EPERM;
+            spin_unlock(&d->shutdown_lock);
+            goto fail_early;
+        }
+    }
+    else
+        d = rcu_lock_current_domain();
 
     memflags |= MEMF_bits(domain_clamp_alloc_bitsize(
         d,
@@ -292,6 +306,9 @@ static long memory_exchange(XEN_GUEST_HA
         if ( hypercall_preempt_check() )
         {
             exch.nr_exchanged = i << in_chunk_order;
+
+            if (unlikely (d != current->domain))
+                spin_unlock(&d->shutdown_lock);
             if ( copy_field_to_guest(arg, &exch, nr_exchanged) )
                 return -EFAULT;
             return hypercall_create_continuation(
@@ -387,6 +404,10 @@ static long memory_exchange(XEN_GUEST_HA
     exch.nr_exchanged = exch.in.nr_extents;
     if ( copy_field_to_guest(arg, &exch, nr_exchanged) )
         rc = -EFAULT;
+
+    if (d != current->domain)
+        spin_unlock(&d->shutdown_lock);
+    rcu_unlock_domain(d);
     return rc;
 
     /*
@@ -399,6 +420,10 @@ static long memory_exchange(XEN_GUEST_HA
         if ( assign_pages(d, page, 0, MEMF_no_refcount) )
             BUG();
 
+    if (d != current->domain)
+        spin_unlock(&d->shutdown_lock);
+    rcu_unlock_domain(d);
+
     /* Free any output pages we managed to allocate. */
     while ( (page = page_list_remove_head(&out_chunk_list)) )
         free_domheap_pages(page, exch.out.extent_order);


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