KVM: lapic: Busy wait for timer to expire when using hv_timer

commit ee66e453db13d4837a0dcf9d43efa7a88603161b upstream.

...now that VMX's preemption timer, i.e. the hv_timer, also adjusts its
programmed time based on lapic_timer_advance_ns.  Without the delay, a
guest can see a timer interrupt arrive before the requested time when
KVM is using the hv_timer to emulate the guest's interrupt.

Fixes: c5ce8235cffa0 ("KVM: VMX: Optimize tscdeadline timer latency")
Cc: <stable@vger.kernel.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 235687f3388faf73fcf93097a8e5882b05762333..6939eba2001ac3b1d6f3d09bf610257876151e0c 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1453,7 +1453,7 @@ static void apic_timer_expired(struct kvm_lapic *apic)
        if (swait_active(q))
                swake_up_one(q);
 
-       if (apic_lvtt_tscdeadline(apic))
+       if (apic_lvtt_tscdeadline(apic) || ktimer->hv_timer_in_use)
                ktimer->expired_tscdeadline = ktimer->tscdeadline;
 }