[Xen-devel] [PATCH] libxl: use named options for tsc_mode

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1320922479 0
# Node ID bc79b560aafa1e4dc42af00e6a326dc651b5636a
# Parent  460b507e15f864dd6712f5040e36538d6e076ae4
libxl: use named options for tsc_mode.

It seems that this knob is expoerted from the hypervisor as a raw
integer (no symbolic names) documented in xen/include/asm-x86. Propagating that
all the way to the end user is hardly friendly (it's bad enough in the
hypercall interface).

Add an enum at the libxl level with a hopefully descriptive set of names.
Deprecate the use of an integer in xl cfg files.

Signed-off-by: Ian Campbell

diff -r 460b507e15f8 -r bc79b560aafa docs/user/xl-domain-config.markdown
--- a/docs/user/xl-domain-config.markdown       Thu Nov 10 10:18:29 2011 +0000
+++ b/docs/user/xl-domain-config.markdown       Thu Nov 10 10:54:39 2011 +0000
@@ -1,4 +1,4 @@
- # xl Domain Configuration
+# xl Domain Configuration
 
 To create a VM (a domain in Xen terminology, sometimes called a guest)
 with xl requires the provision of a domain config file.  Typically
@@ -338,6 +338,29 @@ accept the defaults for these options wh
    extensions (e.g. Windows XP compatibility mode on more modern
    Windows OS).
 
+### Guest Virtual Time Controls
+
+ * `tsc_mode="MODE"`: Specifies how the TSC (Time Stamp Counter)
+   should be provided to the guest (X86 only). Specifying this option as a 
number
+   is deprecated. Options are:
+
+   * `"default"`: guest rdtsc/p executed natively when monotonicity
+     can be guaranteed and emulated otherwise (with frequency scaled
+     if necessary).
+
+   * `"always_emulate"`: guest rdtsc/p always emulated at 1GHz (kernel
+     and user).
+
+   * `"native"`: guest rdtsc always executed natively (no
+     monotonicity/frequency guarantees); guest rdtscp emulated at
+     native frequency if unsupported by h/w, else executed natively.
+
+   * `"native_paravirt"`: same as `native`, except xen manages TSC_AUX
+      register so guest can determine when a restore/migration has
+      occurred and assumes guest obtains/uses pvclock-like mechanism
+      to adjust for monotonicity and frequency changes.
+
+
 ### Support for Paravirtualisation of HVM Guests
 
 The following options allow Paravirtualised features (such as devices)
@@ -546,9 +569,6 @@ certainly belong in a more appropriate s
    enables certain other features which are incompatible with
    migration (currently certain TSC modes XXX ?).
 
- * `tsc_mode=VALUE`: Specifies how the TSC (Time Stamp Counter) should
-   be provided to the guest.  XXX ???
-
  * `pci_msitranslate=BOOLEAN`: XXX
 
  * `pci_power_mgmt=BOOLEAN`: XXX
diff -r 460b507e15f8 -r bc79b560aafa tools/libxl/libxl_dom.c
--- a/tools/libxl/libxl_dom.c   Thu Nov 10 10:18:29 2011 +0000
+++ b/tools/libxl/libxl_dom.c   Thu Nov 10 10:54:39 2011 +0000
@@ -73,12 +73,29 @@ int libxl__build_pre(libxl__gc *gc, uint
               libxl_domain_build_info *info, libxl__domain_build_state *state)
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
+    int tsc_mode;
     xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus);
     xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + 
LIBXL_MAXMEM_CONSTANT);
     if (info->type == LIBXL_DOMAIN_TYPE_PV)
         xc_domain_set_memmap_limit(ctx->xch, domid,
                 (info->max_memkb + info->u.pv.slack_memkb));
-    xc_domain_set_tsc_info(ctx->xch, domid, info->tsc_mode, 0, 0, 0);
+    switch (info->tsc_mode) {
+    case LIBXL_TSC_MODE_DEFAULT:
+        tsc_mode = 0;
+        break;
+    case LIBXL_TSC_MODE_ALWAYS_EMULATE:
+        tsc_mode = 1;
+        break;
+    case LIBXL_TSC_MODE_NATIVE:
+        tsc_mode = 2;
+        break;
+    case LIBXL_TSC_MODE_NATIVE_PARAVIRT:
+        tsc_mode = 3;
+        break;
+    default:
+        abort();
+    }
+    xc_domain_set_tsc_info(ctx->xch, domid, tsc_mode, 0, 0, 0);
     if ( info->disable_migrate )
         xc_domain_disable_migrate(ctx->xch, domid);
 
diff -r 460b507e15f8 -r bc79b560aafa tools/libxl/libxl_types.idl
--- a/tools/libxl/libxl_types.idl       Thu Nov 10 10:18:29 2011 +0000
+++ b/tools/libxl/libxl_types.idl       Thu Nov 10 10:54:39 2011 +0000
@@ -85,6 +85,13 @@ libxl_button = Enumeration("button", [
     (2, "SLEEP"),
     ])
 
+libxl_tsc_mode = Enumeration("tsc_mode", [
+    (0, "default"),
+    (1, "always_emulate"),
+    (2, "native"),
+    (3, "native_paravirt"),
+    ])
+
 #
 # Complex libxl types
 #
@@ -154,7 +161,7 @@ libxl_domain_create_info = Struct("domai
 libxl_domain_build_info = Struct("domain_build_info",[
     ("max_vcpus",       integer),
     ("cur_vcpus",       integer),
-    ("tsc_mode",        integer),
+    ("tsc_mode",        libxl_tsc_mode),
     ("max_memkb",       uint32),
     ("target_memkb",    uint32),
     ("video_memkb",     uint32),
diff -r 460b507e15f8 -r bc79b560aafa tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Thu Nov 10 10:18:29 2011 +0000
+++ b/tools/libxl/xl_cmdimpl.c  Thu Nov 10 10:54:39 2011 +0000
@@ -328,7 +328,7 @@ static void printf_info(int domid,
 
     printf("\t(build_info)\n");
     printf("\t(max_vcpus %d)\n", b_info->max_vcpus);
-    printf("\t(tsc_mode %d)\n", b_info->tsc_mode);
+    printf("\t(tsc_mode %s)\n", libxl_tsc_mode_to_string(b_info->tsc_mode));
     printf("\t(max_memkb %d)\n", b_info->max_memkb);
     printf("\t(target_memkb %d)\n", b_info->target_memkb);
     printf("\t(nomigrate %d)\n", b_info->disable_migrate);
@@ -662,8 +662,23 @@ static void parse_config_data(const char
     if (!xlu_cfg_get_long (config, "nomigrate", &l, 0))
         b_info->disable_migrate = l;
 
-    if (!xlu_cfg_get_long(config, "tsc_mode", &l, 0))
+    if (!xlu_cfg_get_long(config, "tsc_mode", &l, 1)) {
+        fprintf(stderr, "WARNING: specifying \"tsc_mode\" as an integer is 
deprecated. "
+                "Please use the named parameter variant.\n");
+        if (l < LIBXL_TSC_MODE_DEFAULT ||
+            l > LIBXL_TSC_MODE_NATIVE_PARAVIRT) {
+            fprintf(stderr, "ERROR: invalid value %ld for \"tsc_mode\"\n", l);
+            exit (1);
+        }
         b_info->tsc_mode = l;
+    } else if (!xlu_cfg_get_string(config, "tsc_mode", &buf, 0)) {
+        fprintf(stderr, "got a tsc mode string: \"%s\"\n", buf);
+        if (libxl_tsc_mode_from_string(buf, &b_info->tsc_mode)) {
+            fprintf(stderr, "ERROR: invalid value \"%s\" for \"tsc_mode\"\n",
+                    buf);
+            exit (1);
+        }
+    }
 
     if (!xlu_cfg_get_long (config, "videoram", &l, 0))
         b_info->video_memkb = l * 1024;

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