[Xen-devel] [PATCH 4 of 7] x86/mm: wire up sharing ring

[Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>]

 xen/arch/x86/mm/mem_event.c |  41 +++++++++++++++++++++++++++++++++++++++++
 xen/include/public/domctl.h |  20 +++++++++++++++++++-
 xen/include/xen/sched.h     |   3 +++
 3 files changed, 63 insertions(+), 1 deletions(-)


Now that we have an interface close to finalizing, do the necessary plumbing to
set up a ring for reporting failed allocations in the unshare path.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>

diff -r 0c6a33ff829b -r 07f131352fc0 xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c
+++ b/xen/arch/x86/mm/mem_event.c
@@ -432,6 +432,13 @@ static void mem_access_notification(stru
         p2m_mem_access_resume(v->domain);
 }
 
+/* Registered with Xen-bound event channel for incoming notifications. */
+static void mem_sharing_notification(struct vcpu *v, unsigned int port)
+{
+    if ( likely(v->domain->mem_event->share.ring_page != NULL) )
+        mem_sharing_sharing_resume(v->domain);
+}
+
 struct domain *get_mem_event_op_target(uint32_t domain, int *rc)
 {
     struct domain *d;
@@ -599,6 +606,40 @@ int mem_event_domctl(struct domain *d, x
     }
     break;
 
+    case XEN_DOMCTL_MEM_EVENT_OP_SHARING: 
+    {
+        struct mem_event_domain *med = &d->mem_event->share;
+        rc = -EINVAL;
+
+        switch( mec->op )
+        {
+        case XEN_DOMCTL_MEM_EVENT_OP_SHARING_ENABLE:
+        {
+            rc = -ENODEV;
+            /* Only HAP is supported */
+            if ( !hap_enabled(d) )
+                break;
+
+            rc = mem_event_enable(d, mec, med, _VPF_mem_sharing, 
+                                    HVM_PARAM_SHARING_RING_PFN,
+                                    mem_sharing_notification);
+        }
+        break;
+
+        case XEN_DOMCTL_MEM_EVENT_OP_SHARING_DISABLE:
+        {
+            if ( med->ring_page )
+                rc = mem_event_disable(d, med);
+        }
+        break;
+
+        default:
+            rc = -ENOSYS;
+            break;
+        }
+    }
+    break;
+
     default:
         rc = -ENOSYS;
     }
diff -r 0c6a33ff829b -r 07f131352fc0 xen/include/public/domctl.h
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -710,7 +710,7 @@ struct xen_domctl_gdbsx_domstatus {
 /* XEN_DOMCTL_mem_event_op */
 
 /*
-* Domain memory paging
+ * Domain memory paging
  * Page memory in and out.
  * Domctl interface to set up and tear down the 
  * pager<->hypervisor interface. Use XENMEM_paging_op*
@@ -740,6 +740,24 @@ struct xen_domctl_gdbsx_domstatus {
 #define XEN_DOMCTL_MEM_EVENT_OP_ACCESS_ENABLE     0
 #define XEN_DOMCTL_MEM_EVENT_OP_ACCESS_DISABLE    1
 
+/*
+ * Sharing ENOMEM helper.
+ *
+ * As with paging, use the domctl for teardown/setup of the
+ * helper<->hypervisor interface.
+ *
+ * If setup, this ring is used to communicate failed allocations
+ * in the unshare path. XENMEM_sharing_op_resume is used to wake up
+ * vcpus that could not unshare.
+ *
+ * Note that shring can be turned on (as per the domctl below)
+ * *without* this ring being setup.
+ */
+#define XEN_DOMCTL_MEM_EVENT_OP_SHARING           3
+
+#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_ENABLE    0
+#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DISABLE   1
+
 /* Use for teardown/setup of helper<->hypervisor interface for paging, 
  * access and sharing.*/
 struct xen_domctl_mem_event_op {
diff -r 0c6a33ff829b -r 07f131352fc0 xen/include/xen/sched.h
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -643,6 +643,9 @@ static inline struct domain *next_domain
  /* VCPU is blocked due to missing mem_access ring. */
 #define _VPF_mem_access      5
 #define VPF_mem_access       (1UL<<_VPF_mem_access)
+ /* VCPU is blocked due to missing mem_sharing ring. */
+#define _VPF_mem_sharing     6
+#define VPF_mem_sharing      (1UL<<_VPF_mem_sharing)
 
 static inline int vcpu_runnable(struct vcpu *v)
 {

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