From: David Matlack Date: Wed, 9 Mar 2016 00:19:44 +0000 (-0800) Subject: kvm: cap halt polling at exactly halt_poll_ns X-Git-Tag: firefly_0821_release~176^2~4^2~51^2~80 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c9e1bbef7e774dd315fb7f2e239c39cd2bb9674b;p=firefly-linux-kernel-4.4.55.git kvm: cap halt polling at exactly halt_poll_ns commit 313f636d5c490c9741d3f750dc8da33029edbc6b upstream. 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 Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 484079efea5b..7338e30421d8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1961,6 +1961,9 @@ 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); }