On 09/14/2010 11:10 AM, Jan Kiszka wrote:
Am 20.08.2010 10:07, Zachary Amsden wrote:When CPUs with unstable TSCs enter deep C-state, TSC may stop running. This causes us to require resynchronization. Since we can't tell when this may potentially happen, we assume the worst by forcing re-compensation for it at every point the VCPU task is descheduled. Signed-off-by: Zachary Amsden<zamsden@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7fc4a55..52b6c21 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1866,7 +1866,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) } kvm_x86_ops->vcpu_load(vcpu, cpu); - if (unlikely(vcpu->cpu != cpu)) { + if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) { /* Make sure TSC doesn't go backwards */ s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 : native_read_tsc() - vcpu->arch.last_host_tsc;For yet unknown reason, this commit breaks Linux guests here if they are started with only a single VCPU. They hang during boot, obviously no longer receiving interrupts. I'm using kvm-kmod against a 2.6.34 host kernel, so this may be a side effect of the wrapping, though I cannot imagine how. Anyone any ideas?
Most likely, time went backwards, and some 'future - past' calculation resulted in a negative sleep value which was then interpreted as unsigned and resulted in a 2342525634 year sleep.
Does your guest use kvmclock, tsc, or some other time source? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
