Tools: Remove shared page from mem_event/access/paging interfaces

Don't use the superfluous shared page, return the event channel directly as
part of the domctl struct, instead.

In-tree consumers (xenpaging, xen-access) updated. This is an ABI/API change,
so please voice any concerns.

Known pending issues:
- pager could die and its ring page could be used by some other process, yet
  Xen retains the mapping to it.
- use a saner interface for the paging_load buffer.

This change also affects the x86/mm bits in the hypervisor that process the
mem_event setup domctl.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Tim Deegan <tim@xen.org>

4 files changed, 26 insertions, 12 deletions

diff --git a/tools/libxc/xc_mem_access.c b/tools/libxc/xc_mem_access.c
index 3dca355dc1..a3786025f5 100644
--- a/tools/libxc/xc_mem_access.c
+++ b/tools/libxc/xc_mem_access.c
@@ -25,12 +25,18 @@
 
 
 int xc_mem_access_enable(xc_interface *xch, domid_t domain_id,
-                        void *shared_page, void *ring_page)
+                         uint32_t *port, void *ring_page)
 {
+    if ( !port )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
     return xc_mem_event_control(xch, domain_id,
                                 XEN_DOMCTL_MEM_EVENT_OP_ACCESS_ENABLE,
                                 XEN_DOMCTL_MEM_EVENT_OP_ACCESS,
-                                shared_page, ring_page);
+                                port, ring_page);
 }
 
 int xc_mem_access_disable(xc_interface *xch, domid_t domain_id)
diff --git a/tools/libxc/xc_mem_event.c b/tools/libxc/xc_mem_event.c
index a568a52e77..fcca47c764 100644
--- a/tools/libxc/xc_mem_event.c
+++ b/tools/libxc/xc_mem_event.c
@@ -24,19 +24,21 @@
 #include "xc_private.h"
 
 int xc_mem_event_control(xc_interface *xch, domid_t domain_id, unsigned int op,
-                         unsigned int mode, void *page, void *ring_page)
+                         unsigned int mode, uint32_t *port, void *ring_page)
 {
     DECLARE_DOMCTL;
+    int rc;
 
     domctl.cmd = XEN_DOMCTL_mem_event_op;
     domctl.domain = domain_id;
     domctl.u.mem_event_op.op = op;
     domctl.u.mem_event_op.mode = mode;
-
-    domctl.u.mem_event_op.shared_addr = (unsigned long)page;
-    domctl.u.mem_event_op.ring_addr = (unsigned long)ring_page;
+    domctl.u.mem_event_op.ring_addr = (unsigned long) ring_page;
     
-    return do_domctl(xch, &domctl);
+    rc = do_domctl(xch, &domctl);
+    if ( !rc && port )
+        *port = domctl.u.mem_event_op.port;
+    return rc;
 }
 
 int xc_mem_event_memop(xc_interface *xch, domid_t domain_id, 
diff --git a/tools/libxc/xc_mem_paging.c b/tools/libxc/xc_mem_paging.c
index c1330295e7..f8eaa870b3 100644
--- a/tools/libxc/xc_mem_paging.c
+++ b/tools/libxc/xc_mem_paging.c
@@ -25,12 +25,18 @@
 
 
 int xc_mem_paging_enable(xc_interface *xch, domid_t domain_id,
-                        void *shared_page, void *ring_page)
+                         uint32_t *port, void *ring_page)
 {
+    if ( !port )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+        
     return xc_mem_event_control(xch, domain_id,
                                 XEN_DOMCTL_MEM_EVENT_OP_PAGING_ENABLE,
                                 XEN_DOMCTL_MEM_EVENT_OP_PAGING,
-                                shared_page, ring_page);
+                                port, ring_page);
 }
 
 int xc_mem_paging_disable(xc_interface *xch, domid_t domain_id)
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 1b2659f063..823d47a2ac 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -1892,13 +1892,13 @@ int xc_tmem_restore_extra(xc_interface *xch, int dom, int fd);
  * mem_event operations
  */
 int xc_mem_event_control(xc_interface *xch, domid_t domain_id, unsigned int op,
-                         unsigned int mode, void *shared_page, void *ring_page);
+                         unsigned int mode, uint32_t *port, void *ring_page);
 int xc_mem_event_memop(xc_interface *xch, domid_t domain_id, 
                         unsigned int op, unsigned int mode,
                         uint64_t gfn, void *buffer);
 
 int xc_mem_paging_enable(xc_interface *xch, domid_t domain_id,
-                        void *shared_page, void *ring_page);
+                         uint32_t *port, void *ring_page);
 int xc_mem_paging_disable(xc_interface *xch, domid_t domain_id);
 int xc_mem_paging_nominate(xc_interface *xch, domid_t domain_id,
                            unsigned long gfn);
@@ -1908,7 +1908,7 @@ int xc_mem_paging_load(xc_interface *xch, domid_t domain_id,
                         unsigned long gfn, void *buffer);
 
 int xc_mem_access_enable(xc_interface *xch, domid_t domain_id,
-                        void *shared_page, void *ring_page);
+                         uint32_t *port, void *ring_page);
 int xc_mem_access_disable(xc_interface *xch, domid_t domain_id);
 int xc_mem_access_resume(xc_interface *xch, domid_t domain_id,
                          unsigned long gfn);