[Xen-devel] [PATCH 13/13] tools/libxl: Add 'vtsc_khz' option to set guest TSC rate

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

This patch adds an option 'vtsc_khz' to allow users to set vcpu's TSC
rate in KHz. In the case that tsc_mode = 'default', the default value of
'vtsc_khz' option is the host TSC rate which is used when 'vtsc_khz'
option is set to 0 or does not appear in the configuration. In all other
cases of tsc_mode, 'vtsc_khz' option is just ignored.

Another purpose of adding this option is to keep vcpu's TSC rate across
guest reboot. In existing code, a new domain is created from the
configuration of the previous domain which was just rebooted. vcpu's TSC
rate is not stored in the configuration and the host TSC rate is the
used as vcpu's TSC rate. This works fine unless the previous domain was
migrated from another host machine with a different host TSC rate than
the current one.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 tools/libxl/libxl_types.idl |  1 +
 tools/libxl/libxl_x86.c     |  4 +++-
 tools/libxl/xl_cmdimpl.c    | 22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 9f6ec00..91cb0be 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -413,6 +413,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
     ("vcpu_soft_affinity", Array(libxl_bitmap, "num_vcpu_soft_affinity")),
     ("numa_placement",  libxl_defbool),
     ("tsc_mode",        libxl_tsc_mode),
+    ("vtsc_khz",        uint32),
     ("max_memkb",       MemKB),
     ("target_memkb",    MemKB),
     ("video_memkb",     MemKB),
diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
index 896f34c..7baaee4 100644
--- a/tools/libxl/libxl_x86.c
+++ b/tools/libxl/libxl_x86.c
@@ -276,6 +276,7 @@ int libxl__arch_domain_create(libxl__gc *gc, 
libxl_domain_config *d_config,
 {
     int ret = 0;
     int tsc_mode;
+    uint32_t vtsc_khz;
     uint32_t rtc_timeoffset;
     libxl_ctx *ctx = libxl__gc_owner(gc);
 
@@ -300,7 +301,8 @@ int libxl__arch_domain_create(libxl__gc *gc, 
libxl_domain_config *d_config,
     default:
         abort();
     }
-    xc_domain_set_tsc_info(ctx->xch, domid, tsc_mode, 0, 0, 0);
+    vtsc_khz = d_config->b_info.vtsc_khz;
+    xc_domain_set_tsc_info(ctx->xch, domid, tsc_mode, 0, vtsc_khz, 0);
     if (libxl_defbool_val(d_config->b_info.disable_migrate))
         xc_domain_disable_migrate(ctx->xch, domid);
     rtc_timeoffset = d_config->b_info.rtc_timeoffset;
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 2706759..5fabda7 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -1462,6 +1462,28 @@ static void parse_config_data(const char *config_source,
         }
     }
 
+    /* "vtsc_khz" option works only if "tsc_mode" option is
+     * "default". In this case, if "vtsc_khz" option is set to 0, we
+     * will reset it to the host TSC rate. In all other cases, we just
+     * ignore any given value and always set it to 0.
+     */
+    if (!xlu_cfg_get_long(config, "vtsc_khz", &l, 0))
+        b_info->vtsc_khz = l;
+    if (b_info->tsc_mode == LIBXL_TSC_MODE_DEFAULT) {
+        if (b_info->vtsc_khz == 0) {
+            libxl_physinfo physinfo;
+            if (!libxl_get_physinfo(ctx, &physinfo))
+                b_info->vtsc_khz = physinfo.cpu_khz;
+            else
+                fprintf(stderr, "WARNING: cannot get host TSC rate.\n");
+        }
+    } else {
+        fprintf(stderr, "WARNING: ignoring \"vtsc_khz\" option. "
+                "\"vtsc_khz\" option works only if "
+                "\"tsc_mode\" option is \"default\".\n");
+        b_info->vtsc_khz = 0;
+    }
+
     if (!xlu_cfg_get_long(config, "rtc_timeoffset", &l, 0))
         b_info->rtc_timeoffset = l;
 
-- 
2.4.8


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