[Xen-changelog] [xen-3.2-testing] Introduce new vcpu_lock_affinity() and vcpu_unlock_affinity() helper

["Xen patchbot-3.2-testing" <patchbot-3.2-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1201516607 0
# Node ID 3bf41a61a0347b42419a4047f2fcd40fb41df570
# Parent  36a8e6763f3af8938f3c5c60e67cedd8a7ef0120
Introduce new vcpu_lock_affinity() and vcpu_unlock_affinity() helper
functions for use by x86's continue_hypercall_on_cpu().

This has two advantages:
 1. We can lock out ordinary vcpu_set_affinity() commands from dom0.
 2. We avoid the (in this case bogus) check for dom0_vcpus_pin.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
xen-unstable changeset:   16896:7327e1c2a42ced6b1b473e0e738b12e141fb0584
xen-unstable date:        Sat Jan 26 11:25:48 2008 +0000
---
 xen/arch/x86/domain.c   |    9 ++++-----
 xen/common/schedule.c   |   47 +++++++++++++++++++++++++++++++++++++++++------
 xen/include/xen/sched.h |    4 ++++
 3 files changed, 49 insertions(+), 11 deletions(-)

diff -r 36a8e6763f3a -r 3bf41a61a034 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c     Mon Jan 28 10:36:11 2008 +0000
+++ b/xen/arch/x86/domain.c     Mon Jan 28 10:36:47 2008 +0000
@@ -1416,16 +1416,16 @@ static void continue_hypercall_on_cpu_he
 {
     struct cpu_user_regs *regs = guest_cpu_user_regs();
     struct migrate_info *info = v->arch.continue_info;
+    cpumask_t mask = info->saved_affinity;
 
     regs->eax = info->func(info->data);
 
     v->arch.schedule_tail = info->saved_schedule_tail;
-    v->cpu_affinity = info->saved_affinity;
     v->arch.continue_info = NULL;
 
     xfree(info);
 
-    vcpu_set_affinity(v, &v->cpu_affinity);
+    vcpu_unlock_affinity(v, &mask);
     schedule_tail(v);
 }
 
@@ -1433,7 +1433,6 @@ int continue_hypercall_on_cpu(int cpu, l
 {
     struct vcpu *v = current;
     struct migrate_info *info;
-    cpumask_t mask = cpumask_of_cpu(cpu);
     int rc;
 
     if ( cpu == smp_processor_id() )
@@ -1446,12 +1445,12 @@ int continue_hypercall_on_cpu(int cpu, l
     info->func = func;
     info->data = data;
     info->saved_schedule_tail = v->arch.schedule_tail;
-    info->saved_affinity = v->cpu_affinity;
+    info->saved_affinity = cpumask_of_cpu(cpu);
 
     v->arch.schedule_tail = continue_hypercall_on_cpu_helper;
     v->arch.continue_info = info;
 
-    rc = vcpu_set_affinity(v, &mask);
+    rc = vcpu_lock_affinity(v, &info->saved_affinity);
     if ( rc )
     {
         v->arch.schedule_tail = info->saved_schedule_tail;
diff -r 36a8e6763f3a -r 3bf41a61a034 xen/common/schedule.c
--- a/xen/common/schedule.c     Mon Jan 28 10:36:11 2008 +0000
+++ b/xen/common/schedule.c     Mon Jan 28 10:36:47 2008 +0000
@@ -262,12 +262,11 @@ void vcpu_force_reschedule(struct vcpu *
     }
 }
 
-int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity)
-{
-    cpumask_t online_affinity;
-
-    if ( (v->domain->domain_id == 0) && opt_dom0_vcpus_pin )
-        return -EINVAL;
+static int __vcpu_set_affinity(
+    struct vcpu *v, cpumask_t *affinity,
+    bool_t old_lock_status, bool_t new_lock_status)
+{
+    cpumask_t online_affinity, old_affinity;
 
     cpus_and(online_affinity, *affinity, cpu_online_map);
     if ( cpus_empty(online_affinity) )
@@ -275,7 +274,18 @@ int vcpu_set_affinity(struct vcpu *v, cp
 
     vcpu_schedule_lock_irq(v);
 
+    if ( v->affinity_locked != old_lock_status )
+    {
+        BUG_ON(!v->affinity_locked);
+        vcpu_schedule_unlock_irq(v);
+        return -EBUSY;
+    }
+
+    v->affinity_locked = new_lock_status;
+
+    old_affinity = v->cpu_affinity;
     v->cpu_affinity = *affinity;
+    *affinity = old_affinity;
     if ( !cpu_isset(v->processor, v->cpu_affinity) )
         set_bit(_VPF_migrating, &v->pause_flags);
 
@@ -288,6 +298,31 @@ int vcpu_set_affinity(struct vcpu *v, cp
     }
 
     return 0;
+}
+
+int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity)
+{
+    if ( (v->domain->domain_id == 0) && opt_dom0_vcpus_pin )
+        return -EINVAL;
+    return __vcpu_set_affinity(v, affinity, 0, 0);
+}
+
+int vcpu_lock_affinity(struct vcpu *v, cpumask_t *affinity)
+{
+    return __vcpu_set_affinity(v, affinity, 0, 1);
+}
+
+void vcpu_unlock_affinity(struct vcpu *v, cpumask_t *affinity)
+{
+    cpumask_t online_affinity;
+
+    /* Do not fail if no CPU in old affinity mask is online. */
+    cpus_and(online_affinity, *affinity, cpu_online_map);
+    if ( cpus_empty(online_affinity) )
+        *affinity = cpu_online_map;
+
+    if ( __vcpu_set_affinity(v, affinity, 1, 0) != 0 )
+        BUG();
 }
 
 /* Block the currently-executing domain until a pertinent event occurs. */
diff -r 36a8e6763f3a -r 3bf41a61a034 xen/include/xen/sched.h
--- a/xen/include/xen/sched.h   Mon Jan 28 10:36:11 2008 +0000
+++ b/xen/include/xen/sched.h   Mon Jan 28 10:36:47 2008 +0000
@@ -122,6 +122,8 @@ struct vcpu
     bool_t           defer_shutdown;
     /* VCPU is paused following shutdown request (d->is_shutting_down)? */
     bool_t           paused_for_shutdown;
+    /* VCPU affinity is temporarily locked from controller changes? */
+    bool_t           affinity_locked;
 
     unsigned long    pause_flags;
     atomic_t         pause_count;
@@ -483,6 +485,8 @@ void cpu_init(void);
 
 void vcpu_force_reschedule(struct vcpu *v);
 int vcpu_set_affinity(struct vcpu *v, cpumask_t *affinity);
+int vcpu_lock_affinity(struct vcpu *v, cpumask_t *affinity);
+void vcpu_unlock_affinity(struct vcpu *v, cpumask_t *affinity);
 
 void vcpu_runstate_get(struct vcpu *v, struct vcpu_runstate_info *runstate);
 

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