On 03/25/2011 10:44 AM, Joerg Roedel wrote:
The calculation of the tsc_delta value to ensure a forward-going tsc for the guest is a function of the host-tsc. This works as long as the guests tsc_khz is equal to the hosts tsc_khz. With tsc-scaling hardware support this is not longer true and the tsc_delta needs to be calculated--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2126,8 +2126,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_x86_ops->vcpu_load(vcpu, 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; + s64 tsc_delta; + u64 tsc; + + kvm_get_msr(vcpu, MSR_IA32_TSC,&tsc); + tsc_delta = !vcpu->arch.last_guest_tsc ? 0 : + tsc - vcpu->arch.last_guest_tsc; + if (tsc_delta< 0) mark_tsc_unstable("KVM discovered backwards TSC"); if (check_tsc_unstable()) {
Patch is correct, but can this really happen? Won't all machines with scaled tsc also be stable?
Perhaps not multi-board machines. -- 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
