[Xen-devel] [RFC PATCH V3 21/22] Only allow extended event channel on Dom0 and driver domains

[Wei Liu <wei.liu2@xxxxxxxxxx>]

For non-Dom0 domains, add a flag to indicate whether it can use extended event
channel, admins can specify this flag when creating a driver domain.

The rationale behide this option is, a) extended event channel will
consume global mapping space in Xen, b) likely that only Dom0 and driver
domains need this.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/common/domain.c         |    3 +++
 xen/common/domctl.c         |    5 ++++-
 xen/common/event_channel.c  |    6 +++++-
 xen/include/public/domctl.h |    3 +++
 xen/include/xen/sched.h     |    5 +++++
 5 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 07f62b3..293e4b1 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -250,6 +250,9 @@ struct domain *domain_create(
     if ( domcr_flags & DOMCRF_dummy )
         return d;
 
+    if ( domcr_flags & DOMCRF_evtchn_extended )
+        d->evtchn_extended_allowed = 1;
+
     if ( !is_idle_domain(d) )
     {
         if ( (err = xsm_domain_create(XSM_HOOK, d, ssidref)) != 0 )
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index a713ce6..09b9752 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -369,7 +369,8 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         if ( supervisor_mode_kernel ||
              (op->u.createdomain.flags &
              ~(XEN_DOMCTL_CDF_hvm_guest | XEN_DOMCTL_CDF_hap |
-               XEN_DOMCTL_CDF_s3_integrity | XEN_DOMCTL_CDF_oos_off)) )
+               XEN_DOMCTL_CDF_s3_integrity | XEN_DOMCTL_CDF_oos_off |
+               XEN_DOMCTL_CDF_evtchn_extended)) )
             break;
 
         dom = op->domain;
@@ -405,6 +406,8 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
             domcr_flags |= DOMCRF_s3_integrity;
         if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_oos_off )
             domcr_flags |= DOMCRF_oos_off;
+        if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_evtchn_extended )
+            domcr_flags |= DOMCRF_evtchn_extended;
 
         d = domain_create(dom, domcr_flags, op->u.createdomain.ssidref);
         if ( IS_ERR(d) )
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index fac5dc9..56c4fb0 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1291,7 +1291,11 @@ static long evtchn_register_extended(struct 
evtchn_register_extended *reg)
         rc = extended_event_channel;
         break;
     case EVTCHN_EXTENDED_L3:
-        rc = evtchn_register_3level(&reg->u.l3);
+        if ( d->domain_id != 0 &&
+             d->evtchn_extended_allowed == 0 )
+            rc = -EPERM;
+        else
+            rc = evtchn_register_3level(&reg->u.l3);
         break;
     default:
         rc = -EINVAL;
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 74160b0..d5c468e 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -59,6 +59,9 @@ struct xen_domctl_createdomain {
  /* Disable out-of-sync shadow page tables? */
 #define _XEN_DOMCTL_CDF_oos_off       3
 #define XEN_DOMCTL_CDF_oos_off        (1U<<_XEN_DOMCTL_CDF_oos_off)
+ /* Can this domain use extended event channel? */
+#define _XEN_DOMCTL_CDF_evtchn_extended 4
+#define XEN_DOMCTL_CDF_evtchn_extended  (1U<<_XEN_DOMCTL_CDF_evtchn_extended)
     uint32_t flags;
 };
 typedef struct xen_domctl_createdomain xen_domctl_createdomain_t;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 4a3e51c..d0aba9a 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -224,6 +224,8 @@ struct domain
 
     unsigned long   *evtchn_pending;
     unsigned long   *evtchn_mask;
+    /* Can the domain use extended event channel (new ABI)? */
+    bool_t           evtchn_extended_allowed;
 
     struct grant_table *grant_table;
 
@@ -411,6 +413,9 @@ struct domain *domain_create(
  /* DOMCRF_oos_off: dont use out-of-sync optimization for shadow page tables */
 #define _DOMCRF_oos_off         4
 #define DOMCRF_oos_off          (1U<<_DOMCRF_oos_off)
+/* DOMCRF_evtchn_extended: this domain can use extended event channel */
+#define _DOMCRF_evtchn_extended 5
+#define DOMCRF_evtchn_extended  (1U<<_DOMCRF_evtchn_extended)
 
 /*
  * rcu_lock_domain_by_id() is more efficient than get_domain_by_id().
-- 
1.7.10.4


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