xen: use libxendevice model to restrict operations

This patch adds a command-line option (-xen-domid-restrict) which will
use the new libxendevicemodel API to restrict devicemodel [1] operations
to the specified domid. (Such operations are not applicable to the xenpv
machine type).

This patch also adds a tracepoint to allow successful enabling of the
restriction to be monitored.

[1] I.e. operations issued by libxendevicemodel. Operation issued by other
    xen libraries (e.g. libxenforeignmemory) are currently still unrestricted
    but this will be rectified by subsequent patches.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

2 files changed, 21 insertions, 0 deletions

diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
index 2b1733b..7efcdaa 100644
--- a/include/hw/xen/xen.h
+++ b/include/hw/xen/xen.h
@@ -21,6 +21,7 @@ enum xen_mode {
 
 extern uint32_t xen_domid;
 extern enum xen_mode xen_mode;
+extern bool xen_domid_restrict;
 
 extern bool xen_allowed;
 
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index fa990a0..0fcbba8 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -151,6 +151,13 @@ static inline int xendevicemodel_set_mem_type(
     return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
 }
 
+static inline int xendevicemodel_restrict(
+    xendevicemodel_handle *dmod, domid_t domid)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
 
 #undef XC_WANT_COMPAT_DEVICEMODEL_API
@@ -206,6 +213,19 @@ static inline int xen_modified_memory(domid_t domid, uint64_t first_pfn,
     return xendevicemodel_modified_memory(xen_dmod, domid, first_pfn, nr);
 }
 
+static inline int xen_restrict(domid_t domid)
+{
+    int rc = xendevicemodel_restrict(xen_dmod, domid);
+
+    trace_xen_domid_restrict(errno);
+
+    if (errno == ENOTTY) {
+        return 0;
+    }
+
+    return rc;
+}
+
 /* Xen 4.2 through 4.6 */
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701