[PATCH v9 06/11] xen: Introduce XEN_DOMCTL_soft_reset

[Vitaly Kuznetsov <vkuznets@redhat.com>]

New domctl resets state for a domain allowing it to 'start over': register
vcpu_info, switch to FIFO ABI for event channels. Still active grants are
being logged to help debugging misbehaving backends.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
Changes since v8:
- Introduce vcpu_info_reset() helper. [Konrad Rzeszutek Wilk]
- Take shutdown_lock while checking v->paused_for_shutdown in
  domain_soft_reset() [Konrad Rzeszutek Wilk]
---
 xen/common/domain.c         | 44 ++++++++++++++++++++++++++++++++++++--------
 xen/common/domctl.c         |  9 +++++++++
 xen/include/public/domctl.h |  1 +
 xen/include/xen/sched.h     |  2 ++
 4 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 8efef5c..4f805d5 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -110,6 +110,16 @@ static void vcpu_check_shutdown(struct vcpu *v)
     spin_unlock(&d->shutdown_lock);
 }
 
+static void vcpu_info_reset(struct vcpu *v)
+{
+    struct domain *d = v->domain;
+
+    v->vcpu_info = ((v->vcpu_id < XEN_LEGACY_MAX_VCPUS)
+                    ? (vcpu_info_t *)&shared_info(d, vcpu_info[v->vcpu_id])
+                    : &dummy_vcpu_info);
+    v->vcpu_info_mfn = INVALID_MFN;
+}
+
 struct vcpu *alloc_vcpu(
     struct domain *d, unsigned int vcpu_id, unsigned int cpu_id)
 {
@@ -145,10 +155,7 @@ struct vcpu *alloc_vcpu(
         v->runstate.state = RUNSTATE_offline;        
         v->runstate.state_entry_time = NOW();
         set_bit(_VPF_down, &v->pause_flags);
-        v->vcpu_info = ((vcpu_id < XEN_LEGACY_MAX_VCPUS)
-                        ? (vcpu_info_t *)&shared_info(d, vcpu_info[vcpu_id])
-                        : &dummy_vcpu_info);
-        v->vcpu_info_mfn = INVALID_MFN;
+        vcpu_info_reset(v);
         init_waitqueue_vcpu(v);
     }
 
@@ -1010,6 +1017,29 @@ int domain_unpause_by_systemcontroller(struct domain *d)
     return 0;
 }
 
+int domain_soft_reset(struct domain *d)
+{
+    struct vcpu *v;
+    int rc;
+
+    spin_lock(&d->shutdown_lock);
+    for_each_vcpu ( d, v )
+        if ( !v->paused_for_shutdown )
+            return -EINVAL;
+    spin_unlock(&d->shutdown_lock);
+
+    rc = evtchn_reset(d);
+
+    grant_table_warn_active_grants(d);
+
+    for_each_vcpu ( d, v )
+        unmap_vcpu_info(v);
+
+    domain_resume(d);
+
+    return 0;
+}
+
 int vcpu_reset(struct vcpu *v)
 {
     struct domain *d = v->domain;
@@ -1121,8 +1151,7 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned offset)
 
 /*
  * Unmap the vcpu info page if the guest decided to place it somewhere
- * else.  This is only used from arch_domain_destroy, so there's no
- * need to do anything clever.
+ * else. This is used from arch_domain_destroy and domain_soft_reset.
  */
 void unmap_vcpu_info(struct vcpu *v)
 {
@@ -1135,8 +1164,7 @@ void unmap_vcpu_info(struct vcpu *v)
     unmap_domain_page_global((void *)
                              ((unsigned long)v->vcpu_info & PAGE_MASK));
 
-    v->vcpu_info = &dummy_vcpu_info;
-    v->vcpu_info_mfn = INVALID_MFN;
+    vcpu_info_reset(v);
 
     put_page_and_type(mfn_to_page(mfn));
 }
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 7f959f3..41891b1 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -704,6 +704,15 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
         break;
     }
 
+    case XEN_DOMCTL_soft_reset:
+        if ( d == current->domain )
+        {
+            ret = -EINVAL;
+            break;
+        }
+        ret = domain_soft_reset(d);
+        break;
+
     case XEN_DOMCTL_destroydomain:
         ret = domain_kill(d);
         if ( ret == -ERESTART )
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 8b1d6b4..93e85cf 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1130,6 +1130,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_psr_cmt_op                    75
 #define XEN_DOMCTL_monitor_op                    77
 #define XEN_DOMCTL_psr_cat_op                    78
+#define XEN_DOMCTL_soft_reset                    79
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index b29d9e7..18d8b57 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -610,6 +610,8 @@ void domain_shutdown(struct domain *d, u8 reason);
 void domain_resume(struct domain *d);
 void domain_pause_for_debugger(void);
 
+int domain_soft_reset(struct domain *d);
+
 int vcpu_start_shutdown_deferral(struct vcpu *v);
 void vcpu_end_shutdown_deferral(struct vcpu *v);
 
-- 
2.4.3