kvm: writeback SMP TSCs on migration only

commit 6389c45441269baa2873e6feafebd17105ddeaf6
Author: Jan Kiszka <jan.kiszka@siemens.com>
Date:   Mon Mar 1 18:17:26 2010 +0100

    qemu-kvm: Cleanup/fix TSC and PV clock writeback

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Marcelo Tosatti 2010-10-21 13:35:03 -02:00
parent 75b10c4336
commit 384331a61a
1 changed files with 9 additions and 1 deletions

View File

@ -817,7 +817,15 @@ static int kvm_put_msrs(CPUState *env, int level)
kvm_msr_entry_set(&msrs[n++], MSR_LSTAR, env->lstar);
#endif
if (level == KVM_PUT_FULL_STATE) {
kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSC, env->tsc);
/*
* KVM is yet unable to synchronize TSC values of multiple VCPUs on
* writeback. Until this is fixed, we only write the offset to SMP
* guests after migration, desynchronizing the VCPUs, but avoiding
* huge jump-backs that would occur without any writeback at all.
*/
if (smp_cpus == 1 || env->tsc != 0) {
kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSC, env->tsc);
}
kvm_msr_entry_set(&msrs[n++], MSR_KVM_SYSTEM_TIME,
env->system_time_msr);
kvm_msr_entry_set(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);