[Qemu-devel] [PATCH v3 3/3] target-i386: load the migrated vcpu's TSC rate

[Haozhong Zhang <haozhong.zhang@intel.com>]

Set vcpu's TSC rate to the migrated value if the user does not specify a
TSC rate by cpu option 'tsc-freq' and a migrated TSC rate does exist. If
KVM supports TSC scaling, guest programs will observe TSC increasing in
the migrated rate other than the host TSC rate.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
---
 target-i386/kvm.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index aae5e58..2be70df 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -3042,6 +3042,27 @@ int kvm_arch_setup_tsc_khz(CPUState *cs)
     int r;
 
     /*
+     * If a TSC rate is migrated and the user does not specify the
+     * vcpu's TSC rate on the destination, the migrated TSC rate will
+     * be used on the destination after the migration.
+     */
+    if (env->tsc_khz_saved && !env->tsc_khz) {
+        if (kvm_check_extension(cs->kvm_state, KVM_CAP_TSC_CONTROL)) {
+            r = kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz_saved);
+            if (r < 0) {
+                fprintf(stderr, "KVM_SET_TSC_KHZ failed\n");
+            }
+        } else {
+            r = -1;
+            fprintf(stderr, "KVM doesn't support TSC scaling\n");
+        }
+        if (r < 0) {
+            fprintf(stderr, "Use host TSC frequency instead. "
+                    "Guest TSC may be inaccurate.\n");
+        }
+    }
+
+    /*
      * Prepare vcpu's TSC rate to be migrated.
      *
      * - If the user specifies the TSC rate by cpu option 'tsc-freq',
-- 
2.4.8