Commit c9e1bbef authored by David Matlack's avatar David Matlack Committed by Greg Kroah-Hartman

kvm: cap halt polling at exactly halt_poll_ns

commit 313f636d 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: default avatarDavid Matlack <dmatlack@google.com>
Fixes: aca6ff29Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 431c9f01
......@@ -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);
}
......
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