1 files changed, 16 insertions, 24 deletions

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 2d9a9e8..d736b6c 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -892,31 +892,25 @@ asmlinkage void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
 
 void fpsimd_thread_switch(struct task_struct *next)
 {
+	bool wrong_task, wrong_cpu;
+
 	if (!system_supports_fpsimd())
 		return;
+
+	/* Save unsaved fpsimd state, if any: */
+	fpsimd_save();
+
 	/*
-	 * Save the current FPSIMD state to memory, but only if whatever is in
-	 * the registers is in fact the most recent userland FPSIMD state of
-	 * 'current'.
+	 * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's
+	 * state.  For kernel threads, FPSIMD registers are never loaded
+	 * and wrong_task and wrong_cpu will always be true.
 	 */
-	if (current->mm)
-		fpsimd_save();
-
-	if (next->mm) {
-		/*
-		 * If we are switching to a task whose most recent userland
-		 * FPSIMD state is already in the registers of *this* cpu,
-		 * we can skip loading the state from memory. Otherwise, set
-		 * the TIF_FOREIGN_FPSTATE flag so the state will be loaded
-		 * upon the next return to userland.
-		 */
-		bool wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
+	wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
 					&next->thread.uw.fpsimd_state;
-		bool wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();
+	wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();
 
-		update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE,
-				       wrong_task || wrong_cpu);
-	}
+	update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE,
+			       wrong_task || wrong_cpu);
 }
 
 void fpsimd_flush_thread(void)
@@ -1121,9 +1115,8 @@ void kernel_neon_begin(void)
 
 	__this_cpu_write(kernel_neon_busy, true);
 
-	/* Save unsaved task fpsimd state, if any: */
-	if (current->mm)
-		fpsimd_save();
+	/* Save unsaved fpsimd state, if any: */
+	fpsimd_save();
 
 	/* Invalidate any task state remaining in the fpsimd regs: */
 	fpsimd_flush_cpu_state();
@@ -1245,8 +1238,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
 {
 	switch (cmd) {
 	case CPU_PM_ENTER:
-		if (current->mm)
-			fpsimd_save();
+		fpsimd_save();
 		fpsimd_flush_cpu_state();
 		break;
 	case CPU_PM_EXIT: