From 313f636d5c490c9741d3f750dc8da33029edbc6b Mon Sep 17 00:00:00 2001 From: David Matlack Date: Tue, 8 Mar 2016 16:19:44 -0800 Subject: [PATCH] kvm: cap halt polling at exactly halt_poll_ns When growing halt-polling, there is no check that the poll time exceeds the limit. It's possible for vcpu->halt_poll_ns grow once past halt_poll_ns, and stay there until a halt which takes longer than vcpu->halt_poll_ns. For example, booting a Linux guest with halt_poll_ns=11000: ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 0 (shrink 10000) ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 10000 (grow 0) ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (grow 10000) Signed-off-by: David Matlack Fixes: aca6ff29c4063a8d467cdee241e6b3bf7dc4a171 Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a11cfd20a6a0..9102ae172d2a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1952,6 +1952,9 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) else val *= halt_poll_ns_grow; + if (val > halt_poll_ns) + val = halt_poll_ns; + vcpu->halt_poll_ns = val; trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old); } -- 2.20.1