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Re: [Xen-devel] [PATCH v5 7/8] libxl/libxc: Move libxl_get_numainfo()'s hypercall buffer management to libxc

On 03/20/2015 09:56 AM, Ian Campbell wrote:
On Thu, 2015-03-19 at 17:54 -0400, Boris Ostrovsky wrote:
diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
index 411128e..607ae61 100644
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -209,22 +209,49 @@ out:
      return ret;
-int xc_numainfo(xc_interface *xch,
-                xc_numainfo_t *put_info)
+int xc_numainfo(xc_interface *xch, unsigned *max_nodes,
+                xc_meminfo_t *meminfo, uint32_t *distance)
      int ret;
+    DECLARE_HYPERCALL_BOUNCE(meminfo, *max_nodes * sizeof(*meminfo),
+                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
+                             *max_nodes * *max_nodes * sizeof(*distance),
+                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
- sysctl.cmd = XEN_SYSCTL_numainfo;
+    if (meminfo && distance) {
+        if ((ret = xc_hypercall_bounce_pre(xch, meminfo)))
+            goto out;
+        if ((ret = xc_hypercall_bounce_pre(xch, distance)))
+            goto out;
Same comment about handling NULL as before.

In addition what if only one of meminfo and distance is NULL? Is that
valid or do you need a !!meminfo ^ !!distance check?

I want to treat this as as an error here, which is why I have
        } else if (meminfo || distance) {
            errno = EINVAL;
            return -1;

because the hypervisor will only attempt to copy numainfo things when both are valid. Otherwise (i.e. even if only one is a NULL) it will assume that this is a request for size. The alternative would be to add another error there, which I decided not to do.


Rests looks ok.

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