arm64/fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it

The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is
the KVM FPSIMD code.

A following patch will introduce a mechanism to acquire owernship of the
FPSIMD/SVE context for performing context management operations. Rather
than having to export the new helpers to get/put the context, we can just
introduce a new function to combine fpsimd_save() and
fpsimd_flush_cpu_state().

This has also the advantage to remove any external call of fpsimd_save()
and fpsimd_flush_cpu_state(), so they can be turned static.

Lastly, the new function can also be used in the PM notifier.
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/fpsimd.h

@@ -48,8 +48,6 @@ struct task_struct;
 extern void fpsimd_save_state(struct user_fpsimd_state *state);
 extern void fpsimd_load_state(struct user_fpsimd_state *state);
 
-extern void fpsimd_save(void);
-
 extern void fpsimd_thread_switch(struct task_struct *next);
 extern void fpsimd_flush_thread(void);
 
@@ -63,7 +61,7 @@ extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state,
 				     void *sve_state, unsigned int sve_vl);
 
 extern void fpsimd_flush_task_state(struct task_struct *target);
-extern void fpsimd_flush_cpu_state(void);
+extern void fpsimd_save_and_flush_cpu_state(void);
 
 /* Maximum VL that SVE VL-agnostic software can transparently support */
 #define SVE_VL_ARCH_MAX 0x100

arch/arm64/kernel/fpsimd.c

@@ -246,7 +246,7 @@ static void task_fpsimd_load(void)
  *
  * Softirqs (and preemption) must be disabled.
  */
-void fpsimd_save(void)
+static void fpsimd_save(void)
 {
 	struct fpsimd_last_state_struct const *last =
 		this_cpu_ptr(&fpsimd_last_state);
@@ -1122,12 +1122,22 @@ void fpsimd_flush_task_state(struct task_struct *t)
  * Invalidate any task's FPSIMD state that is present on this cpu.
  * This function must be called with softirqs disabled.
  */
-void fpsimd_flush_cpu_state(void)
+static void fpsimd_flush_cpu_state(void)
 {
 	__this_cpu_write(fpsimd_last_state.st, NULL);
 	set_thread_flag(TIF_FOREIGN_FPSTATE);
 }
 
+/*
+ * Save the FPSIMD state to memory and invalidate cpu view.
+ * This function must be called with softirqs (and preemption) disabled.
+ */
+void fpsimd_save_and_flush_cpu_state(void)
+{
+	fpsimd_save();
+	fpsimd_flush_cpu_state();
+}
+
 #ifdef CONFIG_KERNEL_MODE_NEON
 
 DEFINE_PER_CPU(bool, kernel_neon_busy);
@@ -1284,8 +1294,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
 {
 	switch (cmd) {
 	case CPU_PM_ENTER:
-		fpsimd_save();
-		fpsimd_flush_cpu_state();
+		fpsimd_save_and_flush_cpu_state();
 		break;
 	case CPU_PM_EXIT:
 		break;

arch/arm64/kvm/fpsimd.c

@@ -112,9 +112,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
 		u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1];
 
-		/* Clean guest FP state to memory and invalidate cpu view */
-		fpsimd_save();
-		fpsimd_flush_cpu_state();
+		fpsimd_save_and_flush_cpu_state();
 
 		if (guest_has_sve)
 			*guest_zcr = read_sysreg_s(SYS_ZCR_EL12);