queue-4.19/kvm-lapic-busy-wait-for-timer-to-expire-when-using-hv_timer.patch

   1 From ee66e453db13d4837a0dcf9d43efa7a88603161b Mon Sep 17 00:00:00 2001
   2 From: Sean Christopherson <sean.j.christopherson@intel.com>
   3 Date: Tue, 16 Apr 2019 13:32:44 -0700
   4 Subject: KVM: lapic: Busy wait for timer to expire when using hv_timer
   5
   6 From: Sean Christopherson <sean.j.christopherson@intel.com>
   7
   8 commit ee66e453db13d4837a0dcf9d43efa7a88603161b upstream.
   9
  10 ...now that VMX's preemption timer, i.e. the hv_timer, also adjusts its
  11 programmed time based on lapic_timer_advance_ns.  Without the delay, a
  12 guest can see a timer interrupt arrive before the requested time when
  13 KVM is using the hv_timer to emulate the guest's interrupt.
  14
  15 Fixes: c5ce8235cffa0 ("KVM: VMX: Optimize tscdeadline timer latency")
  16 Cc: <stable@vger.kernel.org>
  17 Cc: Wanpeng Li <wanpengli@tencent.com>
  18 Reviewed-by: Liran Alon <liran.alon@oracle.com>
  19 Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
  20 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  22
  23 ---
  24  arch/x86/kvm/lapic.c |    2 +-
  25  1 file changed, 1 insertion(+), 1 deletion(-)
  26
  27 --- a/arch/x86/kvm/lapic.c
  28 +++ b/arch/x86/kvm/lapic.c
  29 @@ -1449,7 +1449,7 @@ static void apic_timer_expired(struct kv
  30         if (swait_active(q))
  31                 swake_up_one(q);
  32
  33 -       if (apic_lvtt_tscdeadline(apic))
  34 +       if (apic_lvtt_tscdeadline(apic) || ktimer->hv_timer_in_use)
  35                 ktimer->expired_tscdeadline = ktimer->tscdeadline;
  36  }
  37