On Thu, Sep 08, 2022 at 04:25:26PM -0700, isaku.yamahata@xxxxxxxxx wrote:
>-
>-``kvm_count_lock``
>-^^^^^^^^^^^^^^^^^^
>-
>-:Type: raw_spinlock_t
>-:Arch: any
>-:Protects: - hardware virtualization enable/disable
>-:Comment: 'raw' because hardware enabling/disabling must be atomic /wrt
>- migration.
>+ - kvm_usage_count
>+ - hardware virtualization enable/disable
>+:Comment: Use cpus_read_lock() for hardware virtualization enable/disable
>+ because hardware enabling/disabling must be atomic /wrt
>+ migration. The lock order is cpus lock => kvm_lock.
Probably "/wrt CPU hotplug" is better.
>
>@@ -5708,8 +5728,18 @@ static void kvm_init_debug(void)
>
> static int kvm_suspend(void)
> {
>- if (kvm_usage_count)
>+ /*
>+ * The caller ensures that CPU hotlug is disabled by
^hotplug
>+ * cpu_hotplug_disable() and other CPUs are offlined. No need for
>+ * locking.
>+ */
>+ lockdep_assert_not_held(&kvm_lock);
>+
>+ if (kvm_usage_count) {
>+ preempt_disable();
> hardware_disable_nolock(NULL);
>+ preempt_enable();
kvm_suspend() is called with interrupt disabled. So, no need to disable
preemption.
/**
* syscore_suspend - Execute all the registered system core suspend callbacks.
*
* This function is executed with one CPU on-line and disabled interrupts.
*/
int syscore_suspend(void)
>+ }
> return 0;
> }
>
>@@ -5723,8 +5753,10 @@ static void kvm_resume(void)
> return; /* FIXME: disable KVM */
>
> if (kvm_usage_count) {
>- lockdep_assert_not_held(&kvm_count_lock);
>+ lockdep_assert_not_held(&kvm_lock);
>+ preempt_disable();
> hardware_enable_nolock((void *)__func__);
>+ preempt_enable();
ditto.
