diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 50f559f..ff2f6cd 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -41,16 +41,6 @@ struct fpsimd_state {
 	unsigned int cpu;
 };
 
-/*
- * Struct for stacking the bottom 'n' FP/SIMD registers.
- */
-struct fpsimd_partial_state {
-	u32		fpsr;
-	u32		fpcr;
-	u32		num_regs;
-	__uint128_t	vregs[32];
-};
-
 
 #if defined(__KERNEL__) && defined(CONFIG_COMPAT)
 /* Masks for extracting the FPSR and FPCR from the FPSCR */
@@ -77,10 +67,6 @@ extern void fpsimd_update_current_state(struct fpsimd_state *state);
 
 extern void fpsimd_flush_task_state(struct task_struct *target);
 
-extern void fpsimd_save_partial_state(struct fpsimd_partial_state *state,
-				      u32 num_regs);
-extern void fpsimd_load_partial_state(struct fpsimd_partial_state *state);
-
 #endif
 
 #endif
diff --git a/arch/arm64/include/asm/fpsimdmacros.h b/arch/arm64/include/asm/fpsimdmacros.h
index a2daf12..0f5fdd3 100644
--- a/arch/arm64/include/asm/fpsimdmacros.h
+++ b/arch/arm64/include/asm/fpsimdmacros.h
@@ -75,59 +75,3 @@
 	ldr	w\tmpnr, [\state, #16 * 2 + 4]
 	fpsimd_restore_fpcr x\tmpnr, \state
 .endm
-
-.macro fpsimd_save_partial state, numnr, tmpnr1, tmpnr2
-	mrs	x\tmpnr1, fpsr
-	str	w\numnr, [\state, #8]
-	mrs	x\tmpnr2, fpcr
-	stp	w\tmpnr1, w\tmpnr2, [\state]
-	adr	x\tmpnr1, 0f
-	add	\state, \state, x\numnr, lsl #4
-	sub	x\tmpnr1, x\tmpnr1, x\numnr, lsl #1
-	br	x\tmpnr1
-	stp	q30, q31, [\state, #-16 * 30 - 16]
-	stp	q28, q29, [\state, #-16 * 28 - 16]
-	stp	q26, q27, [\state, #-16 * 26 - 16]
-	stp	q24, q25, [\state, #-16 * 24 - 16]
-	stp	q22, q23, [\state, #-16 * 22 - 16]
-	stp	q20, q21, [\state, #-16 * 20 - 16]
-	stp	q18, q19, [\state, #-16 * 18 - 16]
-	stp	q16, q17, [\state, #-16 * 16 - 16]
-	stp	q14, q15, [\state, #-16 * 14 - 16]
-	stp	q12, q13, [\state, #-16 * 12 - 16]
-	stp	q10, q11, [\state, #-16 * 10 - 16]
-	stp	q8, q9, [\state, #-16 * 8 - 16]
-	stp	q6, q7, [\state, #-16 * 6 - 16]
-	stp	q4, q5, [\state, #-16 * 4 - 16]
-	stp	q2, q3, [\state, #-16 * 2 - 16]
-	stp	q0, q1, [\state, #-16 * 0 - 16]
-0:
-.endm
-
-.macro fpsimd_restore_partial state, tmpnr1, tmpnr2
-	ldp	w\tmpnr1, w\tmpnr2, [\state]
-	msr	fpsr, x\tmpnr1
-	fpsimd_restore_fpcr x\tmpnr2, x\tmpnr1
-	adr	x\tmpnr1, 0f
-	ldr	w\tmpnr2, [\state, #8]
-	add	\state, \state, x\tmpnr2, lsl #4
-	sub	x\tmpnr1, x\tmpnr1, x\tmpnr2, lsl #1
-	br	x\tmpnr1
-	ldp	q30, q31, [\state, #-16 * 30 - 16]
-	ldp	q28, q29, [\state, #-16 * 28 - 16]
-	ldp	q26, q27, [\state, #-16 * 26 - 16]
-	ldp	q24, q25, [\state, #-16 * 24 - 16]
-	ldp	q22, q23, [\state, #-16 * 22 - 16]
-	ldp	q20, q21, [\state, #-16 * 20 - 16]
-	ldp	q18, q19, [\state, #-16 * 18 - 16]
-	ldp	q16, q17, [\state, #-16 * 16 - 16]
-	ldp	q14, q15, [\state, #-16 * 14 - 16]
-	ldp	q12, q13, [\state, #-16 * 12 - 16]
-	ldp	q10, q11, [\state, #-16 * 10 - 16]
-	ldp	q8, q9, [\state, #-16 * 8 - 16]
-	ldp	q6, q7, [\state, #-16 * 6 - 16]
-	ldp	q4, q5, [\state, #-16 * 4 - 16]
-	ldp	q2, q3, [\state, #-16 * 2 - 16]
-	ldp	q0, q1, [\state, #-16 * 0 - 16]
-0:
-.endm
diff --git a/arch/arm64/include/asm/neon.h b/arch/arm64/include/asm/neon.h
index ad4cdc9..2269322 100644
--- a/arch/arm64/include/asm/neon.h
+++ b/arch/arm64/include/asm/neon.h
@@ -8,12 +8,50 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/compiler.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
 #include <linux/types.h>
 #include <asm/fpsimd.h>
+#include <asm/local.h>
 
 #define cpu_has_neon()		system_supports_fpsimd()
 
-#define kernel_neon_begin()	kernel_neon_begin_partial(32)
-
-void kernel_neon_begin_partial(u32 num_regs);
+void kernel_neon_begin(void);
 void kernel_neon_end(void);
+
+/* FIXME: Backwards compatibility only, should go away: */
+#define kernel_neon_begin_partial(num_regs) kernel_neon_begin()
+
+#ifdef CONFIG_KERNEL_MODE_NEON
+
+extern DEFINE_PER_CPU(local_t, kernel_neon_busy);
+
+/*
+ * Returns true if and only if it is safe to call kernel_neon_begin().
+ * Callers must not assume that the result remains true beyond the next
+ * preempt_enable() or return from softirq context.
+ */
+static bool __maybe_unused kernel_neon_allowed(void)
+{
+	/*
+	 * The per_cpu_ptr() is racy if called with preemption enabled.
+	 * This is not a bug:  per_cpu(kernel_neon_busy) is only set
+	 * when preemption is disabled, so we cannot migrate to another
+	 * CPU while it is set, nor can we migrate to a CPU where it is set.
+	 * So, if we find it clear on some CPU then we're guaranteed to find it
+	 * clear on any CPU we could migrate to.
+	 *
+	 * If we are in between kernel_neon_begin()...kernel_neon_end(), the
+	 * flag will be set, but preemption is also disabled, so we can't
+	 * migrate to another CPU and spuriously see it become false.
+	 */
+	return !(in_irq() || in_nmi()) &&
+		!local_read(this_cpu_ptr(&kernel_neon_busy));
+}
+
+#else /* ! CONFIG_KERNEL_MODE_NEON */
+
+static bool __maybe_unused kernel_neon_allowed(void) { return false; }
+
+#endif /* ! CONFIG_KERNEL_MODE_NEON */
diff --git a/arch/arm64/kernel/entry-fpsimd.S b/arch/arm64/kernel/entry-fpsimd.S
index c44a82f..6a27cd6 100644
--- a/arch/arm64/kernel/entry-fpsimd.S
+++ b/arch/arm64/kernel/entry-fpsimd.S
@@ -41,27 +41,3 @@ ENTRY(fpsimd_load_state)
 	fpsimd_restore x0, 8
 	ret
 ENDPROC(fpsimd_load_state)
-
-#ifdef CONFIG_KERNEL_MODE_NEON
-
-/*
- * Save the bottom n FP registers.
- *
- * x0 - pointer to struct fpsimd_partial_state
- */
-ENTRY(fpsimd_save_partial_state)
-	fpsimd_save_partial x0, 1, 8, 9
-	ret
-ENDPROC(fpsimd_save_partial_state)
-
-/*
- * Load the bottom n FP registers.
- *
- * x0 - pointer to struct fpsimd_partial_state
- */
-ENTRY(fpsimd_load_partial_state)
-	fpsimd_restore_partial x0, 8, 9
-	ret
-ENDPROC(fpsimd_load_partial_state)
-
-#endif
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 06da8ea..22cb8e8 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -21,12 +21,14 @@
 #include <linux/cpu_pm.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/percpu.h>
 #include <linux/sched/signal.h>
 #include <linux/signal.h>
 #include <linux/hardirq.h>
 
 #include <asm/fpsimd.h>
 #include <asm/cputype.h>
+#include <asm/local.h>
 
 #define FPEXC_IOF	(1 << 0)
 #define FPEXC_DZF	(1 << 1)
@@ -230,49 +232,43 @@ void fpsimd_flush_task_state(struct task_struct *t)
 
 #ifdef CONFIG_KERNEL_MODE_NEON
 
-static DEFINE_PER_CPU(struct fpsimd_partial_state, hardirq_fpsimdstate);
-static DEFINE_PER_CPU(struct fpsimd_partial_state, softirq_fpsimdstate);
+DEFINE_PER_CPU(local_t, kernel_neon_busy);
 
 /*
  * Kernel-side NEON support functions
  */
-void kernel_neon_begin_partial(u32 num_regs)
+void kernel_neon_begin(void)
 {
 	if (WARN_ON(!system_supports_fpsimd()))
 		return;
-	if (in_interrupt()) {
-		struct fpsimd_partial_state *s = this_cpu_ptr(
-			in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);
 
-		BUG_ON(num_regs > 32);
-		fpsimd_save_partial_state(s, roundup(num_regs, 2));
-	} else {
-		/*
-		 * Save the userland FPSIMD state if we have one and if we
-		 * haven't done so already. Clear fpsimd_last_state to indicate
-		 * that there is no longer userland FPSIMD state in the
-		 * registers.
-		 */
-		preempt_disable();
-		if (current->mm &&
-		    !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
-			fpsimd_save_state(&current->thread.fpsimd_state);
+	BUG_ON(!kernel_neon_allowed());
+
+	preempt_disable();
+	local_set(this_cpu_ptr(&kernel_neon_busy), 1);
+
+	/*
+	 * If there is unsaved task fpsimd state in the CPU, save it
+	 * and invalidate the copy stored in the fpsimd regs:
+	 */
+	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE)) {
+		fpsimd_save_state(&current->thread.fpsimd_state);
 		this_cpu_write(fpsimd_last_state, NULL);
 	}
 }
-EXPORT_SYMBOL(kernel_neon_begin_partial);
+EXPORT_SYMBOL(kernel_neon_begin);
 
 void kernel_neon_end(void)
 {
+	long busy;
+
 	if (!system_supports_fpsimd())
 		return;
-	if (in_interrupt()) {
-		struct fpsimd_partial_state *s = this_cpu_ptr(
-			in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);
-		fpsimd_load_partial_state(s);
-	} else {
-		preempt_enable();
-	}
+
+	busy = local_xchg(this_cpu_ptr(&kernel_neon_busy), 0);
+	WARN_ON(!busy);	/* No matching kernel_neon_begin()? */
+
+	preempt_enable();
 }
 EXPORT_SYMBOL(kernel_neon_end);
 
