xen/domain: Remove function pointers from domain pause helpers

Function pointer calls are expensive (especially with Spectre v2 protections),
and all these do are select between the sync and nosync helpers.  Pass a
boolean instead, and use direct calls everywhere.

Pause/unpause operations on behalf of dom0 are not fastpaths, so avoid
exposing the __domain_pause_by_systemcontroller() internal.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 093bb4403f8b4103d0b2dc2549721b017c1a9d2f..2048ebad86ffdfdabbf761ed526c46e4e28045ef 100644 (file)
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1226,15 +1226,18 @@ int vcpu_unpause_by_systemcontroller(struct vcpu *v)
     return 0;
 }
 
-static void do_domain_pause(struct domain *d,
-                            void (*sleep_fn)(struct vcpu *v))
+static void _domain_pause(struct domain *d, bool sync)
 {
     struct vcpu *v;
 
     atomic_inc(&d->pause_count);
 
-    for_each_vcpu( d, v )
-        sleep_fn(v);
+    if ( sync )
+        for_each_vcpu ( d, v )
+            vcpu_sleep_sync(v);
+    else
+        for_each_vcpu ( d, v )
+            vcpu_sleep_nosync(v);
 
     arch_domain_pause(d);
 }
@@ -1242,12 +1245,12 @@ static void do_domain_pause(struct domain *d,
 void domain_pause(struct domain *d)
 {
     ASSERT(d != current->domain);
-    do_domain_pause(d, vcpu_sleep_sync);
+    _domain_pause(d, true /* sync */);
 }
 
 void domain_pause_nosync(struct domain *d)
 {
-    do_domain_pause(d, vcpu_sleep_nosync);
+    _domain_pause(d, false /* nosync */);
 }
 
 void domain_unpause(struct domain *d)
@@ -1261,8 +1264,7 @@ void domain_unpause(struct domain *d)
             vcpu_wake(v);
 }
 
-int __domain_pause_by_systemcontroller(struct domain *d,
-                                       void (*pause_fn)(struct domain *d))
+static int _domain_pause_by_systemcontroller(struct domain *d, bool sync)
 {
     int old, new, prev = d->controller_pause_count;
 
@@ -1281,11 +1283,21 @@ int __domain_pause_by_systemcontroller(struct domain *d,
         prev = cmpxchg(&d->controller_pause_count, old, new);
     } while ( prev != old );
 
-    pause_fn(d);
+    _domain_pause(d, sync);
 
     return 0;
 }
 
+int domain_pause_by_systemcontroller(struct domain *d)
+{
+    return _domain_pause_by_systemcontroller(d, true /* sync */);
+}
+
+int domain_pause_by_systemcontroller_nosync(struct domain *d)
+{
+    return _domain_pause_by_systemcontroller(d, false /* nosync */);
+}
+
 int domain_unpause_by_systemcontroller(struct domain *d)
 {
     int old, new, prev = d->controller_pause_count;

diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 28146ee404e6cfc9c0dc51037d1c1d773be67deb..37f78cc4c4c9a3ef690b9a71ff533e0d688ed7f9 100644 (file)
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -920,26 +920,21 @@ static inline bool vcpu_cpu_dirty(const struct vcpu *v)
 
 void vcpu_block(void);
 void vcpu_unblock(struct vcpu *v);
+
 void vcpu_pause(struct vcpu *v);
 void vcpu_pause_nosync(struct vcpu *v);
 void vcpu_unpause(struct vcpu *v);
+
 int vcpu_pause_by_systemcontroller(struct vcpu *v);
 int vcpu_unpause_by_systemcontroller(struct vcpu *v);
 
 void domain_pause(struct domain *d);
 void domain_pause_nosync(struct domain *d);
 void domain_unpause(struct domain *d);
+
+int domain_pause_by_systemcontroller(struct domain *d);
+int domain_pause_by_systemcontroller_nosync(struct domain *d);
 int domain_unpause_by_systemcontroller(struct domain *d);
-int __domain_pause_by_systemcontroller(struct domain *d,
-                                       void (*pause_fn)(struct domain *d));
-static inline int domain_pause_by_systemcontroller(struct domain *d)
-{
-    return __domain_pause_by_systemcontroller(d, domain_pause);
-}
-static inline int domain_pause_by_systemcontroller_nosync(struct domain *d)
-{
-    return __domain_pause_by_systemcontroller(d, domain_pause_nosync);
-}
 
 /* domain_pause() but safe against trying to pause current. */
 int __must_check domain_pause_except_self(struct domain *d);