libxl,xl: add max_event_channels option to xl configuration file

Add the 'max_event_channels' option to the xl configuration file to
limit the number of event channels that domain may use.

Plumb this option through to libxl via a new libxl_build_info field
and call xc_domain_set_max_evtchn() in the post build stage of domain
creation.

A new LIBXL_HAVE_BUILDINFO_EVENT_CHANNELS #define indicates that this
new field is available.

The default value of 1023 limits the domain to using the minimum
amount of global mapping pages and at most 5 xenheap pages.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 6e2252afbe..356f920a6d 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -268,6 +268,13 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
     if (rc)
         return rc;
 
+    rc = xc_domain_set_max_evtchn(ctx->xch, domid, info->event_channels);
+    if (rc) {
+        LOG(ERROR, "Failed to set event channel limit to %d (%d)",
+            info->event_channels, rc);
+        return ERROR_FAIL;
+    }
+
     libxl_cpuid_apply_policy(ctx, domid);
     if (info->cpuid != NULL)
         libxl_cpuid_set(ctx, domid, info->cpuid);