On Fri, Sep 12, 2025 at 03:35:29PM +0800, Hou Wenlong wrote:
>The commit a377ac1cd9d7b ("x86/entry: Move user return notifier out of
>loop") moved fire_user_return_notifiers() into the section with
>interrupts disabled, so the callback kvm_on_user_return() cannot be
>interrupted by kvm_arch_disable_virtualization_cpu() now. Therefore,
>remove the outdated comments and local_irq_save()/local_irq_restore()
>code in kvm_on_user_return().
>
>Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
>---
> arch/x86/kvm/x86.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>index 33fba801b205..10afbacb1851 100644
>--- a/arch/x86/kvm/x86.c
>+++ b/arch/x86/kvm/x86.c
>@@ -568,18 +568,12 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
> struct kvm_user_return_msrs *msrs
> = container_of(urn, struct kvm_user_return_msrs, urn);
> struct kvm_user_return_msr_values *values;
>- unsigned long flags;
>
>- /*
>- * Disabling irqs at this point since the following code could be
>- * interrupted and executed through kvm_arch_disable_virtualization_cpu()
>- */
>- local_irq_save(flags);
>- if (msrs->registered) {
>- msrs->registered = false;
>- user_return_notifier_unregister(urn);
>- }
>- local_irq_restore(flags);
>+ lockdep_assert_irqs_disabled();
kvm_offline_cpu() may call into this function. But I am not sure if interrupts
are disabled in that path.
Documentation/core-api/cpu_hotplug.rst says that callbacks in the ONLINE section
are invoked with interrupts and preemption enabled.
>+
>+ msrs->registered = false;
>+ user_return_notifier_unregister(urn);
>+
> for (slot = 0; slot < kvm_nr_uret_msrs; ++slot) {
> values = &msrs->values[slot];
> if (values->host != values->curr) {
>--
>2.31.1
>
>
