kvm: Cap halt polling at kvm->max_halt_poll_ns

commit 258785ef08b323bddd844b4926a32c2b2045a1b0 upstream.

When growing halt-polling, there is no check that the poll time exceeds
the per-VM limit. It's possible for vcpu->halt_poll_ns to grow past
kvm->max_halt_poll_ns and stay there until a halt which takes longer
than kvm->halt_poll_ns.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org>
Message-Id: <20210506152442.4010298-1-venkateshs@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2d2dfb8b51eabdc623acc023f68b3087d854a689..1b80ab4f3cba5d8a6785927788691b601eb4deca 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2734,8 +2734,8 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
        if (val < grow_start)
                val = grow_start;
 
-       if (val > halt_poll_ns)
-               val = halt_poll_ns;
+       if (val > vcpu->kvm->max_halt_poll_ns)
+               val = vcpu->kvm->max_halt_poll_ns;
 
        vcpu->halt_poll_ns = val;
 out: