[xen staging] xen/domain: Remove function pointers from domain pause helpers

[patchbot@xxxxxxx]

commit 52c06465fc7286cb06743adf15f10b0759ed8f4e
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Oct 28 04:07:02 2021 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Dec 17 17:03:54 2021 +0000

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/domain.c     | 30 +++++++++++++++++++++---------
 xen/include/xen/sched.h | 15 +++++----------
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 093bb4403f..2048ebad86 100644
--- 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 28146ee404..37f78cc4c4 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);
--
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