On 07/07/2016 14:18, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> We will go to vcpu_run() loop after L0 emulates VMRESUME which maybe
> incur kvm_sched_out and kvm_sched_in operations since cond_resched()
> will be called once need resched. Preemption timer will be reprogrammed
> if vCPU is scheduled to a different pCPU. Then the preemption timer
> bit of vmcs02 will be set if L0 enable preemption timer to run L1 even
> if L1 doesn't enable preemption timer to run L2.
>
> This patch fix it by don't reprogram preemption timer of vmcs02 if L1's
> vCPU is scheduled on diffent pCPU when we are in the way to vmresume
> nested guest, and fallback to hrtimer based emulated method.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx>
> Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> Cc: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> v3 -> v4:
> * fallback to hrtimer based emulated method when in the way to vmresume nested guest
>
> arch/x86/kvm/x86.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0cc6cf8..05137c0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2743,8 +2743,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> mark_tsc_unstable("KVM discovered backwards TSC");
>
> if (kvm_lapic_hv_timer_in_use(vcpu) &&
> + (is_guest_mode(vcpu) ||
> kvm_x86_ops->set_hv_timer(vcpu,
> - kvm_get_lapic_tscdeadline_msr(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,
>
Thanks, this is good as a fallback. I'll try to fix it by getting the
pin-based execution controls right but if I fail this patch is okay.
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
--
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
