commit 6389c45441269baa2873e6feafebd17105ddeaf6
Author: Jan Kiszka <[email protected]>
Date: Mon Mar 1 18:17:26 2010 +0100
qemu-kvm: Cleanup/fix TSC and PV clock writeback
Signed-off-by: Marcelo Tosatti <[email protected]>
---
target-i386/kvm.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 06474d6..e2f7e2e 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -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);
--
1.7.2.1
--
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