On 30/08/2016 10:14, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> TSC_OFFSET will be adjusted if discovers TSC backward during vCPU load.
> The preemption timer which will leverage guest tsc to reprogram its
> preemption timer value is also reprogrammed if vCPU is scheded in to
> a different pCPU. However, current implementation reprogram preemption
> timer before TSC_OFFSET is adjusted to the right value, this will result
> in preemption timer also backward and fire prematurity.
>
> This patch fix it by adjusting TSC_OFFSET before reprogramming preemption
> timer if TSC backward.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 19f9f9e..699f872 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2743,16 +2743,16 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> if (tsc_delta < 0)
> mark_tsc_unstable("KVM discovered backwards TSC");
>
> - if (kvm_lapic_hv_timer_in_use(vcpu) &&
> - kvm_x86_ops->set_hv_timer(vcpu,
> - kvm_get_lapic_tscdeadline_msr(vcpu)))
> - kvm_lapic_switch_to_sw_timer(vcpu);
> if (check_tsc_unstable()) {
> u64 offset = kvm_compute_tsc_offset(vcpu,
> vcpu->arch.last_guest_tsc);
> kvm_x86_ops->write_tsc_offset(vcpu, offset);
> vcpu->arch.tsc_catchup = 1;
> }
> + if (kvm_lapic_hv_timer_in_use(vcpu) &&
> + kvm_x86_ops->set_hv_timer(vcpu,
> + kvm_get_lapic_tscdeadline_msr(vcpu)))
> + kvm_lapic_switch_to_sw_timer(vcpu);
> /*
> * On a host with synchronized TSC, there is no need to update
> * kvmclock on vcpu->cpu migration
>
Queued for 4.8, thanks.
Paolo
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