x86: warn if arch_flush_lazy_mmu_cpu is called in preemptible context

Impact: Catch cases where lazy MMU state is active in a preemtible context

arch_flush_lazy_mmu_cpu() has been changed to disable preemption so
the checks in enter/leave will never trigger. Put the preemtible()
check into arch_flush_lazy_mmu_cpu() to catch such cases.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index dcba6c567a2a..c6520a4e85d4 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -273,6 +273,7 @@ void arch_flush_lazy_mmu_mode(void)
         preempt_disable();
 
         if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
+                WARN_ON(preempt_count() == 1);
                 arch_leave_lazy_mmu_mode();
                 arch_enter_lazy_mmu_mode();
         }
@@ -285,6 +286,7 @@ void arch_flush_lazy_cpu_mode(void)
         preempt_disable();
 
         if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
+                WARN_ON(preempt_count() == 1);
                 arch_leave_lazy_cpu_mode();
                 arch_enter_lazy_cpu_mode();
         }