Add DOMCTL to limit the number of event channels a domain may use

Add XEN_DOMCTL_set_max_evtchn which may be used during domain creation to
set the maximum event channel port a domain may use.  This may be used to
limit the amount of Xen resources (global mapping space and xenheap) that
a domain may use for event channels.

A domain that does not have a limit set may use all the event channels
supported by the event channel ABI in use.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Keir Fraser <keir@xen.org>

2 files changed, 14 insertions, 0 deletions

diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 4c5b2bbbbd..d4e479f92b 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -852,6 +852,17 @@ struct xen_domctl_set_broken_page_p2m {
 typedef struct xen_domctl_set_broken_page_p2m xen_domctl_set_broken_page_p2m_t;
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_broken_page_p2m_t);
 
+/*
+ * XEN_DOMCTL_set_max_evtchn: sets the maximum event channel port
+ * number the guest may use.  Use this limit the amount of resources
+ * (global mapping space, xenheap) a guest may use for event channels.
+ */
+struct xen_domctl_set_max_evtchn {
+    uint32_t max_port;
+};
+typedef struct xen_domctl_set_max_evtchn xen_domctl_set_max_evtchn_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_max_evtchn_t);
+
 struct xen_domctl {
     uint32_t cmd;
 #define XEN_DOMCTL_createdomain                   1
@@ -920,6 +931,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_set_broken_page_p2m           67
 #define XEN_DOMCTL_setnodeaffinity               68
 #define XEN_DOMCTL_getnodeaffinity               69
+#define XEN_DOMCTL_set_max_evtchn                70
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
@@ -975,6 +987,7 @@ struct xen_domctl {
         struct xen_domctl_set_access_required access_required;
         struct xen_domctl_audit_p2m         audit_p2m;
         struct xen_domctl_set_virq_handler  set_virq_handler;
+        struct xen_domctl_set_max_evtchn    set_max_evtchn;
         struct xen_domctl_gdbsx_memio       gdbsx_guest_memio;
         struct xen_domctl_set_broken_page_p2m set_broken_page_p2m;
         struct xen_domctl_gdbsx_pauseunp_vcpu gdbsx_pauseunp_vcpu;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index ca7e41712d..c2588a5f86 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -291,6 +291,7 @@ struct domain
     struct evtchn   *evtchn;                         /* first bucket only */
     struct evtchn  **evtchn_group[NR_EVTCHN_GROUPS]; /* all other buckets */
     unsigned int     max_evtchns;
+    unsigned int     max_evtchn_port;
     spinlock_t       event_lock;
     const struct evtchn_port_ops *evtchn_port_ops;
     struct evtchn_fifo_domain *evtchn_fifo;