[PATCH 2/4] kvm: Allow invtsc migration if tsc-khz is set explicitly

Eduardo Habkost
2016-12-27T19:21:18Z

We can safely allow a VM to be migrated with invtsc enabled if
tsc-khz is set explicitly, because QEMU already refuses to start
if it can't set the TSC frequency to the configured value.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
target/i386/kvm.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index a26290f..6a51399 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -962,15 +962,16 @@ int kvm_arch_init_vcpu(CPUState *cs)
has_msr_mcg_ext_ctl = has_msr_feature_control = true;
}

- if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) &&
- invtsc_mig_blocker == NULL) {
- /* for migration */
- error_setg(&invtsc_mig_blocker,
- "State blocked by non-migratable CPU device"
- " (invtsc flag)");
- migrate_add_blocker(invtsc_mig_blocker);
- /* for savevm */
- vmstate_x86_cpu.unmigratable = 1;
+ if (!env->user_tsc_khz) {
+ if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) &&
+ invtsc_mig_blocker == NULL) {
+ /* for migration */
+ error_setg(&invtsc_mig_blocker,
+ "State blocked by non-migratable CPU device"
+ " (invtsc flag)");
+ migrate_add_blocker(invtsc_mig_blocker);
+ /* for savevm */
+ vmstate_x86_cpu.unmigratable = 1;
}

cpuid_data.cpuid.padding = 0;
--
2.7.4