Commit 313f636d authored Mar 08, 2016 by David Matlack Committed by Paolo Bonzini Mar 09, 2016

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 <dmatlack@google.com>
Fixes: aca6ff29
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 9522b37f

virt/kvm/kvm_main.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}