---

yaml
---
r: 258261
b: refs/heads/master
c: f8f2a85
h: refs/heads/master
i:
  258259: 4fe6e24
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 08409c33d6fdb43fa19d7dbdafd4f280b7835592
+refs/heads/master: f8f2a8522a88aacd62a310ce49e8dac530d1b403

trunk/arch/arm/kernel/asm-offsets.c

@@ -59,6 +59,9 @@ int main(void)
   DEFINE(TI_TP_VALUE,		offsetof(struct thread_info, tp_value));
   DEFINE(TI_FPSTATE,		offsetof(struct thread_info, fpstate));
   DEFINE(TI_VFPSTATE,		offsetof(struct thread_info, vfpstate));
+#ifdef CONFIG_SMP
+  DEFINE(VFP_CPU,		offsetof(union vfp_state, hard.cpu));
+#endif
 #ifdef CONFIG_ARM_THUMBEE
   DEFINE(TI_THUMBEE_STATE,	offsetof(struct thread_info, thumbee_state));
 #endif

trunk/arch/arm/vfp/vfphw.S

@@ -82,19 +82,22 @@ ENTRY(vfp_support_entry)
 	ldr	r4, [r3, r11, lsl #2]	@ vfp_current_hw_state pointer
 	bic	r5, r1, #FPEXC_EX	@ make sure exceptions are disabled
 	cmp	r4, r10			@ this thread owns the hw context?
+#ifndef CONFIG_SMP
+	@ For UP, checking that this thread owns the hw context is
+	@ sufficient to determine that the hardware state is valid.
 	beq	vfp_hw_state_valid
 
+	@ On UP, we lazily save the VFP context.  As a different
+	@ thread wants ownership of the VFP hardware, save the old
+	@ state if there was a previous (valid) owner.
+
 	VFPFMXR	FPEXC, r5		@ enable VFP, disable any pending
 					@ exceptions, so we can get at the
 					@ rest of it
 
-#ifndef CONFIG_SMP
-	@ Save out the current registers to the old thread state
-	@ No need for SMP since this is not done lazily
-
 	DBGSTR1	"save old state %p", r4
-	cmp	r4, #0
-	beq	no_old_VFP_process
+	cmp	r4, #0			@ if the vfp_current_hw_state is NULL
+	beq	vfp_reload_hw		@ then the hw state needs reloading
 	VFPFSTMIA r4, r5		@ save the working registers
 	VFPFMRX	r5, FPSCR		@ current status
 #ifndef CONFIG_CPU_FEROCEON
@@ -107,11 +110,33 @@ ENTRY(vfp_support_entry)
 1:
 #endif
 	stmia	r4, {r1, r5, r6, r8}	@ save FPEXC, FPSCR, FPINST, FPINST2
-					@ and point r4 at the word at the
-					@ start of the register dump
+vfp_reload_hw:
+
+#else
+	@ For SMP, if this thread does not own the hw context, then we
+	@ need to reload it.  No need to save the old state as on SMP,
+	@ we always save the state when we switch away from a thread.
+	bne	vfp_reload_hw
+
+	@ This thread has ownership of the current hardware context.
+	@ However, it may have been migrated to another CPU, in which
+	@ case the saved state is newer than the hardware context.
+	@ Check this by looking at the CPU number which the state was
+	@ last loaded onto.
+	ldr	ip, [r10, #VFP_CPU]
+	teq	ip, r11
+	beq	vfp_hw_state_valid
+
+vfp_reload_hw:
+	@ We're loading this threads state into the VFP hardware. Update
+	@ the CPU number which contains the most up to date VFP context.
+	str	r11, [r10, #VFP_CPU]
+
+	VFPFMXR	FPEXC, r5		@ enable VFP, disable any pending
+					@ exceptions, so we can get at the
+					@ rest of it
 #endif
 
-no_old_VFP_process:
 	DBGSTR1	"load state %p", r10
 	str	r10, [r3, r11, lsl #2]	@ update the vfp_current_hw_state pointer
 					@ Load the saved state back into the VFP

trunk/arch/arm/vfp/vfpmodule.c

@@ -34,19 +34,52 @@ void vfp_null_entry(void);
 
 void (*vfp_vector)(void) = vfp_null_entry;
 
+/*
+ * Dual-use variable.
+ * Used in startup: set to non-zero if VFP checks fail
+ * After startup, holds VFP architecture
+ */
+unsigned int VFP_arch;
+
 /*
  * The pointer to the vfpstate structure of the thread which currently
  * owns the context held in the VFP hardware, or NULL if the hardware
  * context is invalid.
+ *
+ * For UP, this is sufficient to tell which thread owns the VFP context.
+ * However, for SMP, we also need to check the CPU number stored in the
+ * saved state too to catch migrations.
  */
 union vfp_state *vfp_current_hw_state[NR_CPUS];
 
 /*
- * Dual-use variable.
- * Used in startup: set to non-zero if VFP checks fail
- * After startup, holds VFP architecture
+ * Is 'thread's most up to date state stored in this CPUs hardware?
+ * Must be called from non-preemptible context.
  */
-unsigned int VFP_arch;
+static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread)
+{
+#ifdef CONFIG_SMP
+	if (thread->vfpstate.hard.cpu != cpu)
+		return false;
+#endif
+	return vfp_current_hw_state[cpu] == &thread->vfpstate;
+}
+
+/*
+ * Force a reload of the VFP context from the thread structure.  We do
+ * this by ensuring that access to the VFP hardware is disabled, and
+ * clear last_VFP_context.  Must be called from non-preemptible context.
+ */
+static void vfp_force_reload(unsigned int cpu, struct thread_info *thread)
+{
+	if (vfp_state_in_hw(cpu, thread)) {
+		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+		vfp_current_hw_state[cpu] = NULL;
+	}
+#ifdef CONFIG_SMP
+	thread->vfpstate.hard.cpu = NR_CPUS;
+#endif
+}
 
 /*
  * Per-thread VFP initialization.
@@ -60,6 +93,9 @@ static void vfp_thread_flush(struct thread_info *thread)
 
 	vfp->hard.fpexc = FPEXC_EN;
 	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
+#ifdef CONFIG_SMP
+	vfp->hard.cpu = NR_CPUS;
+#endif
 
 	/*
 	 * Disable VFP to ensure we initialize it first.  We must ensure
@@ -90,6 +126,9 @@ static void vfp_thread_copy(struct thread_info *thread)
 
 	vfp_sync_hwstate(parent);
 	thread->vfpstate = parent->vfpstate;
+#ifdef CONFIG_SMP
+	thread->vfpstate.hard.cpu = NR_CPUS;
+#endif
 }
 
 /*
@@ -135,17 +174,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
 		 * case the thread migrates to a different CPU. The
 		 * restoring is done lazily.
 		 */
-		if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu]) {
+		if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu])
 			vfp_save_state(vfp_current_hw_state[cpu], fpexc);
-			vfp_current_hw_state[cpu]->hard.cpu = cpu;
-		}
-		/*
-		 * Thread migration, just force the reloading of the
-		 * state on the new CPU in case the VFP registers
-		 * contain stale data.
-		 */
-		if (thread->vfpstate.hard.cpu != cpu)
-			vfp_current_hw_state[cpu] = NULL;
 #endif
 
 		/*
@@ -449,15 +479,15 @@ static void vfp_pm_init(void)
 static inline void vfp_pm_init(void) { }
 #endif /* CONFIG_PM */
 
+/*
+ * Ensure that the VFP state stored in 'thread->vfpstate' is up to date
+ * with the hardware state.
+ */
 void vfp_sync_hwstate(struct thread_info *thread)
 {
 	unsigned int cpu = get_cpu();
 
-	/*
-	 * If the thread we're interested in is the current owner of the
-	 * hardware VFP state, then we need to save its state.
-	 */
-	if (vfp_current_hw_state[cpu] == &thread->vfpstate) {
+	if (vfp_state_in_hw(cpu, thread)) {
 		u32 fpexc = fmrx(FPEXC);
 
 		/*
@@ -471,36 +501,13 @@ void vfp_sync_hwstate(struct thread_info *thread)
 	put_cpu();
 }
 
+/* Ensure that the thread reloads the hardware VFP state on the next use. */
 void vfp_flush_hwstate(struct thread_info *thread)
 {
 	unsigned int cpu = get_cpu();
 
-	/*
-	 * If the thread we're interested in is the current owner of the
-	 * hardware VFP state, then we need to save its state.
-	 */
-	if (vfp_current_hw_state[cpu] == &thread->vfpstate) {
-		u32 fpexc = fmrx(FPEXC);
+	vfp_force_reload(cpu, thread);
 
-		fmxr(FPEXC, fpexc & ~FPEXC_EN);
-
-		/*
-		 * Set the context to NULL to force a reload the next time
-		 * the thread uses the VFP.
-		 */
-		vfp_current_hw_state[cpu] = NULL;
-	}
-
-#ifdef CONFIG_SMP
-	/*
-	 * For SMP we still have to take care of the case where the thread
-	 * migrates to another CPU and then back to the original CPU on which
-	 * the last VFP user is still the same thread. Mark the thread VFP
-	 * state as belonging to a non-existent CPU so that the saved one will
-	 * be reloaded in the above case.
-	 */
-	thread->vfpstate.hard.cpu = NR_CPUS;
-#endif
 	put_cpu();
 }
 
@@ -519,8 +526,7 @@ static int vfp_hotplug(struct notifier_block *b, unsigned long action,
 	void *hcpu)
 {
 	if (action == CPU_DYING || action == CPU_DYING_FROZEN) {
-		unsigned int cpu = (long)hcpu;
-		vfp_current_hw_state[cpu] = NULL;
+		vfp_force_reload((long)hcpu, current_thread_info());
 	} else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
 		vfp_enable(NULL);
 	return NOTIFY_OK;