[PATCH RFC 3/4] tools/libxc: Add APIs to create and get the PV ring page

[Aravindh Puthiyaparambil <aravindp@cisco.com>]

Add two APIs, xc_mem_access_create_ring_page() and
xc_mem_access_get_ring_mfn(). The mem_access listener needs to call
xc_mem_access_create_ring_page() before enabling mem_access for PV
domains. This is not needed for HVM domains as the page is created
during domain creation time. It can then call
xc_mem_access_get_ring_mfn() to get the mfn of the created page to map
in. This is requivalent to xc_get_hvm_param(HVM_PARAM_ACCESS_RING_PFN)
for HVM domains.

Signed-off-by: Aravindh Puthiyaparambil <aravindp@cisco.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
---
 tools/libxc/xc_mem_access.c | 29 +++++++++++++++++++++++++++++
 tools/libxc/xenctrl.h       | 17 ++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/xc_mem_access.c b/tools/libxc/xc_mem_access.c
index f436e69..b85af0d 100644
--- a/tools/libxc/xc_mem_access.c
+++ b/tools/libxc/xc_mem_access.c
@@ -97,6 +97,35 @@ int xc_get_mem_access(xc_interface *xch,
     return rc;
 }
 
+int xc_mem_access_create_ring_page(xc_interface *xch, domid_t domain_id)
+{
+    xen_mem_access_op_t mao =
+    {
+        .op    = XENMEM_access_op_create_ring_page,
+        .domid = domain_id
+    };
+
+    return do_memory_op(xch, XENMEM_access_op, &mao, sizeof(mao));
+}
+
+int xc_mem_access_get_ring_mfn(xc_interface *xch, domid_t domain_id,
+                               unsigned long *mfn)
+{
+    int rc;
+    xen_mem_access_op_t mao =
+    {
+        .op    = XENMEM_access_op_get_ring_mfn,
+        .domid = domain_id
+    };
+
+    rc = do_memory_op(xch, XENMEM_access_op, &mao, sizeof(mao));
+
+    if ( !rc )
+        *mfn = mao.pfn;
+
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 02129f7..a1c743d 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -2050,7 +2050,10 @@ int xc_mem_access_resume(xc_interface *xch, domid_t domain_id);
 /*
  * Set a range of memory to a specific access.
  * Allowed types are XENMEM_access_default, XENMEM_access_n, any combination of
- * XENMEM_access_ + (rwx), and XENMEM_access_rx2rw
+ * XENMEM_access_ + (rwx), XENMEM_access_rx2rw and XENMEM_access_n2rwx for HVM
+ * domains.
+ * Allowed types are XENMEM_access_default, XENMEM_access_r, XENMEM_access_rw,
+ * XENMEM_access_rwx and XENMEM_access_rx2rw for PV domains.
  */
 int xc_set_mem_access(xc_interface *xch, domid_t domain_id,
                       xenmem_access_t access, uint64_t first_pfn,
@@ -2062,6 +2065,18 @@ int xc_set_mem_access(xc_interface *xch, domid_t domain_id,
 int xc_get_mem_access(xc_interface *xch, domid_t domain_id,
                       uint64_t pfn, xenmem_access_t *access);
 
+/*
+ * Create the ring page for PV domains. This has to be called before calling
+ * xc_mem_access_enable(). This should not be called for HVM domains
+ */
+int xc_mem_access_create_ring_page(xc_interface *xch, domid_t domain_id);
+
+/*
+ * Get the mfn of the ring page for PV domains
+ */
+int xc_mem_access_get_ring_mfn(xc_interface *xch, domid_t domain_id,
+                               unsigned long *mfn);
+
 /***
  * Memory sharing operations.
  *
-- 
1.9.1