KVM: PPC: Book3S HV: Add check for module parameter halt_poll_ns

The kvm module parameter halt_poll_ns defines the global maximum halt
polling interval and can be dynamically changed by writing to the
/sys/module/kvm/parameters/halt_poll_ns sysfs file. However in kvm-hv
this module parameter value is only ever checked when we grow the current
polling interval for the given vcore. This means that if we decrease the
halt_poll_ns value below the current polling interval we won't see any
effect unless we try to grow the polling interval above the new max at some
point or it happens to be shrunk below the halt_poll_ns value.

Update the halt polling code so that we always check for a new module param
value of halt_poll_ns and set the current halt polling interval to it if
it's currently greater than the new max. This means that it's redundant to
also perform this check in the grow_halt_poll_ns() function now.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index f0d22ced3e1f4cde40b99014e483f3a73fe549cc..0b0ca272a13cc997891f57693da97e1b9f7fd990 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2599,9 +2599,6 @@ static void grow_halt_poll_ns(struct kvmppc_vcore *vc)
                vc->halt_poll_ns = 10000;
        else
                vc->halt_poll_ns *= halt_poll_ns_grow;
-
-       if (vc->halt_poll_ns > halt_poll_ns)
-               vc->halt_poll_ns = halt_poll_ns;
 }
 
 static void shrink_halt_poll_ns(struct kvmppc_vcore *vc)
@@ -2721,6 +2718,8 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
                else if (vc->halt_poll_ns < halt_poll_ns &&
                                block_ns < halt_poll_ns)
                        grow_halt_poll_ns(vc);
+               if (vc->halt_poll_ns > halt_poll_ns)
+                       vc->halt_poll_ns = halt_poll_ns;
        } else
                vc->halt_poll_ns = 0;