[PATCH 1/5] xen/domain: Remove function pointers from domain pause helpers

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Retpolines are expensive, 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.

This actually compiles smaller than before:

  $ ../scripts/bloat-o-meter xen-syms-before xen-syms-after
  add/remove: 3/1 grow/shrink: 0/5 up/down: 250/-273 (-23)
  Function                                     old     new   delta
  _domain_pause                                  -     115    +115
  domain_pause_by_systemcontroller               -      69     +69
  domain_pause_by_systemcontroller_nosync        -      66     +66
  domain_kill                                  426     398     -28
  domain_resume                                246     214     -32
  domain_pause_except_self                     189     141     -48
  domain_pause                                  59      10     -49
  domain_pause_nosync                           59       7     -52
  __domain_pause_by_systemcontroller            64       -     -64

despite GCC's best efforts.  The new _domain_pause_by_systemcontroller()
really should not be inlined, considering that the difference is only the
setup of the sync boolean to pass to _domain_pause(), and there are plenty of
registers to spare.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/common/domain.c     | 31 ++++++++++++++++++++++---------
 xen/include/xen/sched.h | 15 +++++----------
 2 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 56d47dd66478..562872cdf87a 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1234,15 +1234,18 @@ 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 /* or nosync */)
 {
     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);
 }
@@ -1250,12 +1253,12 @@ 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)
@@ -1269,8 +1272,8 @@ 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 /* or nosync */)
 {
     int old, new, prev = d->controller_pause_count;
 
@@ -1289,11 +1292,21 @@ 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 28146ee404e6..37f78cc4c4c9 100644
--- 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);
-- 
2.11.0