From f1ff89ec4447c4e39d275a1ca3de43eed2a92745 Mon Sep 17 00:00:00 2001 From: Roman Kagan Date: Thu, 20 Jul 2017 17:26:40 +0300 Subject: [PATCH] kvm: x86: hyperv: avoid livelock in oneshot SynIC timers MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If the SynIC timer message delivery fails due to SINT message slot being busy, there's no point to attempt starting the timer again until we're notified of the slot being released by the guest (via EOM or EOI). Even worse, when a oneshot timer fails to deliver its message, its re-arming with an expiration time in the past leads to immediate retry of the delivery, and so on, without ever letting the guest vcpu to run and release the slot, which results in a livelock. To avoid that, only start the timer when there's no timer message pending delivery. When there is, meaning the slot is busy, the processing will be restarted upon notification from the guest that the slot is released. Signed-off-by: Roman Kagan Signed-off-by: Radim Krčmář --- arch/x86/kvm/hyperv.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 2695a34fa1c5..337b6d2730fa 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -649,9 +649,10 @@ void kvm_hv_process_stimers(struct kvm_vcpu *vcpu) } if ((stimer->config & HV_STIMER_ENABLE) && - stimer->count) - stimer_start(stimer); - else + stimer->count) { + if (!stimer->msg_pending) + stimer_start(stimer); + } else stimer_cleanup(stimer); } } -- 2.20.1