[PATCH v8 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>
---
 xen/common/domain.c         | 29 ++++++++++++++++++++++++++---
 xen/common/domctl.c         |  9 +++++++++
 xen/include/public/domctl.h |  1 +
 xen/include/xen/sched.h     |  2 ++
 4 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 3bc52e6..ade80ff 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1010,6 +1010,26 @@ int domain_unpause_by_systemcontroller(struct domain *d)
     return 0;
 }
 
+int domain_soft_reset(struct domain *d)
+{
+    struct vcpu *v;
+
+    for_each_vcpu ( d, v )
+        if ( !v->paused_for_shutdown )
+            return -EINVAL;
+
+    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;
@@ -1121,12 +1141,12 @@ 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)
 {
     unsigned long mfn;
+    struct domain *d = v->domain;
 
     if ( v->vcpu_info_mfn == INVALID_MFN )
         return;
@@ -1135,7 +1155,10 @@ 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 = ((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;
 
     put_page_and_type(mfn_to_page(mfn));
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index ce517a7..8cb6a2a 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -703,6 +703,15 @@ 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 bc45ea5..5b4ba6b 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1114,6 +1114,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_setvnumainfo                  74
 #define XEN_DOMCTL_psr_cmt_op                    75
 #define XEN_DOMCTL_monitor_op                    77
+#define XEN_DOMCTL_soft_reset                    78
 #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 d810e1c..1120741 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -609,6 +609,8 @@ 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);
 
-- 
2.4.2