diff -r 86640f3de07f tools/libxc/xc_hcall_buf.c
--- a/tools/libxc/xc_hcall_buf.c	Mon Nov 01 10:03:55 2010 +0000
+++ b/tools/libxc/xc_hcall_buf.c	Mon Nov 01 10:21:05 2010 +0000
@@ -120,17 +120,22 @@ int xc__hypercall_bounce_pre(xc_interfac
      */
     if ( b->ubuf == NULL )
     {
+        fprintf(stderr, "%s user buffer is NULL at %d\n", __func__, __LINE__);
         b->hbuf = NULL;
         return 0;
     }
 
     p = xc__hypercall_buffer_alloc(xch, b, b->sz);
     if ( p == NULL )
+    {
+        fprintf(stderr, "%s failed at %d\n", __func__, __LINE__);
         return -1;
+    }
 
     if ( b->dir == XC_HYPERCALL_BUFFER_BOUNCE_IN || b->dir == XC_HYPERCALL_BUFFER_BOUNCE_BOTH )
         memcpy(b->hbuf, b->ubuf, b->sz);
 
+    fprintf(stderr, "%s bounced %zd bytes from user buf %p into hcall buf %p\n", __func__, b->sz, b->ubuf, b->hbuf);
     return 0;
 }
 
@@ -143,11 +148,15 @@ void xc__hypercall_bounce_post(xc_interf
         abort();
 
     if ( b->hbuf == NULL )
+    {
+        fprintf(stderr, "%s hcall buffer is NULL at %d (%p, %p)\n", __func__, __LINE__, b->hbuf, b->ubuf);
         return;
+    }
 
     if ( b->dir == XC_HYPERCALL_BUFFER_BOUNCE_OUT || b->dir == XC_HYPERCALL_BUFFER_BOUNCE_BOTH )
         memcpy(b->ubuf, b->hbuf, b->sz);
 
+    fprintf(stderr, "%s bounced %zd bytes back from hcall buf %p into user buf %p\n", __func__, b->sz, b->hbuf, b->ubuf);
     xc__hypercall_buffer_free(xch, b);
 }
 
diff -r 86640f3de07f tools/libxc/xc_pm.c
--- a/tools/libxc/xc_pm.c	Mon Nov 01 10:03:55 2010 +0000
+++ b/tools/libxc/xc_pm.c	Mon Nov 01 10:21:05 2010 +0000
@@ -128,20 +128,32 @@ int xc_pm_get_cxstat(xc_interface *xch, 
     DECLARE_NAMED_HYPERCALL_BOUNCE(residencies, &cxpt->residencies, 0, XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
     int max_cx, ret;
 
-    if( !cxpt || !(cxpt->triggers) || !(cxpt->residencies) )
-        return -EINVAL;
+    if( !cxpt || !(cxpt->triggers) || !(cxpt->residencies) ) {
+        fprintf(stderr, "%s failing at %d\n", __func__, __LINE__);
+        errno = EINVAL;
+        return -1;
+    }
 
     if ( (ret = xc_pm_get_max_cx(xch, cpuid, &max_cx)) )
+    {
+        fprintf(stderr, "%s failing at %d\n", __func__, __LINE__);
         goto unlock_0;
+    }
 
     HYPERCALL_BOUNCE_SET_SIZE(triggers, max_cx * sizeof(uint64_t));
     HYPERCALL_BOUNCE_SET_SIZE(residencies, max_cx * sizeof(uint64_t));
 
     ret = -1;
     if ( xc_hypercall_bounce_pre(xch, triggers) )
+    {
+        fprintf(stderr, "%s failing at %d\n", __func__, __LINE__);
         goto unlock_0;
+    }
     if ( xc_hypercall_bounce_pre(xch, residencies) )
+    {
+        fprintf(stderr, "%s failing at %d\n", __func__, __LINE__);
         goto unlock_1;
+    }
 
     sysctl.cmd = XEN_SYSCTL_get_pmstat;
     sysctl.u.get_pmstat.type = PMSTAT_get_cxstat;
@@ -150,7 +162,10 @@ int xc_pm_get_cxstat(xc_interface *xch, 
     set_xen_guest_handle(sysctl.u.get_pmstat.u.getcx.residencies, residencies);
 
     if ( (ret = xc_sysctl(xch, &sysctl)) )
+    {
+        fprintf(stderr, "%s failing at %d\n", __func__, __LINE__);
         goto unlock_2;
+    }
 
     cxpt->nr = sysctl.u.get_pmstat.u.getcx.nr;
     cxpt->last = sysctl.u.get_pmstat.u.getcx.last;
@@ -166,6 +181,7 @@ unlock_1:
 unlock_1:
     xc_hypercall_bounce_post(xch, triggers);
 unlock_0:
+        fprintf(stderr, "%s done returning %d\n", __func__, ret);
     return ret;
 }
 
diff -r 86640f3de07f tools/misc/xenpm.c
--- a/tools/misc/xenpm.c	Mon Nov 01 10:03:55 2010 +0000
+++ b/tools/misc/xenpm.c	Mon Nov 01 10:21:05 2010 +0000
@@ -115,12 +115,15 @@ static int get_cxstat_by_cpuid(xc_interf
     if ( !cxstat )
         return -EINVAL;
 
+    fprintf(stderr, "get_cxstat_by_cpuid: max_cx %d for cpuid %d\n", max_cx_num, cpuid);
+
     cxstat->triggers = malloc(max_cx_num * sizeof(uint64_t));
     if ( !cxstat->triggers )
         return -ENOMEM;
     cxstat->residencies = malloc(max_cx_num * sizeof(uint64_t));
     if ( !cxstat->residencies )
     {
+        fprintf(stderr, "failed to allocate residencies, freeing triggers\n");
         free(cxstat->triggers);
         return -ENOMEM;
     }
@@ -129,13 +132,14 @@ static int get_cxstat_by_cpuid(xc_interf
     if( ret )
     {
         int temp = errno;
+        fprintf(stderr, "xc_pm_get_cx_stat failed %d %d, freeing buffers\n", ret, errno);
         free(cxstat->triggers);
         free(cxstat->residencies);
         cxstat->triggers = NULL;
         cxstat->residencies = NULL;
         return temp;
     }
-
+    fprintf(stderr, "get_cx_stat_by_cpuid succeeded for cpu %d\n", cpuid);
     return 0;
 }