On 08/08/2019 16:29, Steven Price wrote:

On 04/08/2019 10:53, Marc Zyngier wrote:

quoted

On Fri,  2 Aug 2019 15:50:17 +0100
Steven Price [off-list ref] wrote:

quoted

Enable paravirtualization features when running under a hypervisor
supporting the PV_TIME_ST hypercall.

For each (v)CPU, we ask the hypervisor for the location of a shared
page which the hypervisor will use to report stolen time to us. We set
pv_time_ops to the stolen time function which simply reads the stolen
value from the shared page for a VCPU. We guarantee single-copy
atomicity using READ_ONCE which means we can also read the stolen
time for another VCPU than the currently running one while it is
potentially being updated by the hypervisor.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kernel/Makefile |   1 +
 arch/arm64/kernel/kvm.c    | 155 +++++++++++++++++++++++++++++++++++++

[...]

quoted

quoted

+static int __init kvm_guest_init(void)
+{
+	int ret = 0;
+
+	if (!has_kvm_steal_clock())
+		return 0;
+
+	ret = kvm_arm_init_stolen_time();
+	if (ret)
+		return ret;
+
+	pv_ops.time.steal_clock = kvm_steal_clock;
+
+	static_key_slow_inc(&paravirt_steal_enabled);
+	if (steal_acc)
+		static_key_slow_inc(&paravirt_steal_rq_enabled);
+
+	pr_info("using stolen time PV\n");
+
+	return 0;
+}
+early_initcall(kvm_guest_init);

Is there any reason why we wouldn't directly call into this rather than
using an initcall?

I'm not sure where the direct call would go - any pointers?

I'd be temped to say arch/arm64/kernel/time.c:time_init(), provided that
there is no issue with the CPU hotplug lock (I remember hitting that a
while ago).

	M.
-- 
Jazz is not dead, it just smells funny...

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