[Qemu-devel] [PATCH v5 2/3] target-i386: reorganize TSC rate setting code

[Haozhong Zhang]

Following two changes are made to the TSC rate setting code in
kvm_arch_init_vcpu():
 * The code is moved to a new function kvm_arch_set_tsc_khz().
 * If setting user-specified TSC rate fails and the host TSC rate is
   inconsistent with the user-specified one, print a warning message.

Signed-off-by: Haozhong Zhang <address@hidden>
---
 target-i386/kvm.c | 45 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 9e4d27f..6a1acb4 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -524,6 +524,41 @@ static bool hyperv_enabled(X86CPU *cpu)
             cpu->hyperv_runtime);
 }
 
+/**
+ * Ask KVM to set vcpu's TSC rate to X86_CPU(cs)->env.tsc_khz.
+ *
+ * Returns: 0        if successful;
+ *          -ENOTSUP if KVM_CAP_TSC_CONTROL is unavailable;
+ *          -EIO     if KVM_SET_TSC_KHZ fails.
+ */
+static int kvm_arch_set_tsc_khz(CPUState *cs)
+{
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+    int has_tsc_control, r = 0;
+
+    if (!env->tsc_khz) {
+        return 0;
+    }
+
+    has_tsc_control = kvm_check_extension(cs->kvm_state, KVM_CAP_TSC_CONTROL);
+    if (has_tsc_control) {
+        r = kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz);
+    }
+
+    if (!has_tsc_control || r < 0) {
+        r = kvm_check_extension(cs->kvm_state, KVM_CAP_GET_TSC_KHZ) ?
+            kvm_vcpu_ioctl(cs, KVM_GET_TSC_KHZ) : -ENOTSUP;
+        if (r <= 0 || r != env->tsc_khz) {
+            error_report("warning: TSC frequency mismatch between "
+                         "VM and host, and TSC scaling unavailable");
+            return has_tsc_control ? -EIO : -ENOTSUP;
+        }
+    }
+
+    return 0;
+}
+
 static Error *invtsc_mig_blocker;
 
 #define KVM_MAX_CPUID_ENTRIES  100
@@ -823,13 +858,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
         return r;
     }
 
-    r = kvm_check_extension(cs->kvm_state, KVM_CAP_TSC_CONTROL);
-    if (r && env->tsc_khz) {
-        r = kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz);
-        if (r < 0) {
-            fprintf(stderr, "KVM_SET_TSC_KHZ failed\n");
-            return r;
-        }
+    if (kvm_arch_set_tsc_khz(cs) == -EIO) {
+        fprintf(stderr, "KVM_SET_TSC_KHZ failed\n");
+        return -EIO;
     }
 
     /*
-- 
2.4.8