tools: introduce a new parameter to set a predefined rdm boundary

Previously we always fix that predefined boundary as 2G to handle
conflict between memory and rdm, but now this predefined boundar
can be changes with the parameter "rdm_mem_boundary" in .cfg file.

CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Checked-by: Ian Jackson <ian.jackson@eu.citrix.com>

docs/man/xl.cfg.pod.5

@@ -845,6 +845,28 @@ More information about Xen gfx_passthru feature is available
 on the XenVGAPassthrough L<http://wiki.xen.org/wiki/XenVGAPassthrough>
 wiki page.
 
+=item B<rdm_mem_boundary=MBYTES>
+
+Number of megabytes to set a boundary for checking rdm conflict.
+
+When RDM conflicts with RAM, RDM probably scatter the whole RAM space.
+Especially multiple RDM entries would worsen this to lead a complicated
+memory layout. So here we're trying to figure out a simple solution to
+avoid breaking existing layout. So when a conflict occurs,
+
+    #1. Above a predefined boundary
+        - move lowmem_end below reserved region to solve conflict;
+
+    #2. Below a predefined boundary
+        - Check strict/relaxed policy.
+        "strict" policy leads to fail libxl. Note when both policies
+        are specified on a given region, 'strict' is always preferred.
+        "relaxed" policy issue a warning message and also mask this
+        entry INVALID to indicate we shouldn't expose this entry to
+        hvmloader.
+
+Here the default is 2G.
+
 =item B<dtdev=[ "DTDEV_PATH", "DTDEV_PATH", ... ]>
 
 Specifies the host device tree nodes to passthrough to this guest. Each

tools/libxl/libxl.h

@@ -909,6 +909,12 @@ const char *libxl_defbool_to_string(libxl_defbool b);
 #define LIBXL_TIMER_MODE_DEFAULT -1
 #define LIBXL_MEMKB_DEFAULT ~0ULL
 
+/*
+ * We'd like to set a memory boundary to determine if we need to check
+ * any overlap with reserved device memory.
+ */
+#define LIBXL_RDM_MEM_BOUNDARY_MEMKB_DEFAULT (2048 * 1024)
+
 #define LIBXL_MS_VM_GENID_LEN 16
 typedef struct {
     uint8_t bytes[LIBXL_MS_VM_GENID_LEN];

tools/libxl/libxl_create.c

@@ -54,6 +54,10 @@ void libxl__rdm_setdefault(libxl__gc *gc, libxl_domain_build_info *b_info)
 {
     if (b_info->u.hvm.rdm.policy == LIBXL_RDM_RESERVE_POLICY_INVALID)
         b_info->u.hvm.rdm.policy = LIBXL_RDM_RESERVE_POLICY_RELAXED;
+
+    if (b_info->u.hvm.rdm_mem_boundary_memkb == LIBXL_MEMKB_DEFAULT)
+        b_info->u.hvm.rdm_mem_boundary_memkb =
+                            LIBXL_RDM_MEM_BOUNDARY_MEMKB_DEFAULT;
 }
 
 int libxl__domain_build_info_setdefault(libxl__gc *gc,

tools/libxl/libxl_dom.c

@@ -930,12 +930,6 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
     int ret, rc = ERROR_FAIL;
     uint64_t mmio_start, lowmem_end, highmem_end;
     libxl_domain_build_info *const info = &d_config->b_info;
-    /*
-     * Currently we fix this as 2G to guarantee how to handle
-     * our rdm policy. But we'll provide a parameter to set
-     * this dynamically.
-     */
-    uint64_t rdm_mem_boundary = 0x80000000;
 
     memset(&args, 0, sizeof(struct xc_hvm_build_args));
     /* The params from the configuration file are in Mb, which are then
@@ -974,7 +968,7 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
     args.mmio_start = mmio_start;
 
     rc = libxl__domain_device_construct_rdm(gc, d_config,
-                                            rdm_mem_boundary,
+                                            info->u.hvm.rdm_mem_boundary_memkb*1024,
                                             &args);
     if (rc) {
         LOG(ERROR, "checking reserved device memory failed");

tools/libxl/libxl_types.idl

@@ -503,6 +503,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                        ("ms_vm_genid",      libxl_ms_vm_genid),
                                        ("serial_list",      libxl_string_list),
                                        ("rdm", libxl_rdm_reserve),
+                                       ("rdm_mem_boundary_memkb", MemKB),
                                        ])),
                  ("pv", Struct(None, [("kernel", string),
                                       ("slack_memkb", MemKB),

tools/libxl/xl_cmdimpl.c

@@ -1583,6 +1583,9 @@ static void parse_config_data(const char *config_source,
                     exit(1);
             }
         }
+
+        if (!xlu_cfg_get_long (config, "rdm_mem_boundary", &l, 0))
+            b_info->u.hvm.rdm_mem_boundary_memkb = l * 1024;
         break;
     case LIBXL_DOMAIN_TYPE_PV:
     {