[RFC 04/11] powerpc: kvm: introduce a kthread on primary thread to anti tickless

kernelfans at gmail.com kernelfans at gmail.com
Fri Oct 17 06:29:53 AEDT 2014

(This patch is a place holder.)

If there is only one vcpu thread is ready(the other vcpu thread can
wait for it to execute), the primary thread can enter tickless mode,
which causes the primary keeps running, so the secondary has no
opportunity to exit to host, even they have other tsk on them.

Introduce a kthread (anti_tickless) on primary, so when there is only
one vcpu thread on primary, the secondary can resort to anti_tickless
to keep the primary out of tickless mode.
(I thought that anti_tickless thread can goto NAP, so we can let the
secondary run).

Signed-off-by: Liu Ping Fan <pingfank at linux.vnet.ibm.com>
 arch/powerpc/kernel/sysfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index a2595dd..f0b110e 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -575,9 +575,11 @@ static ssize_t __used store_kvm_enable(struct device *dev,
 	if (!test_bit(core, &kvm_on_core))
 		for (thr = 1; thr< threads_per_core; thr++)
 			if (cpu_online(thr * threads_per_core + thr))
-				cpumask_set_cpu(thr * threads_per_core + thr, &stop_cpus);
+				cpumask_set_cpu(core * threads_per_core + thr, &stop_cpus);
 	stop_machine(xics_migrate_irqs_away_secondary, NULL, &stop_cpus);
+	/* fixme, create a kthread on primary hwthread to handle tickless mode */
+	//kthread_create_on_cpu(prevent_tickless, NULL, core * threads_per_core, "ppckvm_prevent_tickless");
 	set_bit(core, &kvm_on_core);
 	return count;

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