This second patch is separate because it could be wrong,
like I am not sure about how kernel thread migration works,
and it is even allowing simd in preemptible kernel code.
Signed-off-by: Shawn Landden <sh...@git.icu>
---
arch/powerpc/include/asm/simd.h | 8 +++++
arch/powerpc/include/asm/switch_to.h | 10 ++----
arch/powerpc/kernel/process.c | 50 ++++++++++++++++++++++++++--
3 files changed, 57 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/include/asm/simd.h b/arch/powerpc/include/asm/simd.h
index 2c02ad531..7b582b07e 100644
--- a/arch/powerpc/include/asm/simd.h
+++ b/arch/powerpc/include/asm/simd.h
@@ -7,7 +7,15 @@
* It's always ok in process context (ie "not interrupt")
* but it is sometimes ok even from an irq.
*/
+#ifdef CONFIG_ALTIVEC
+extern bool irq_simd_usable(void);
static __must_check inline bool may_use_simd(void)
{
return irq_simd_usable();
}
+#else
+static inline bool may_use_simd(void)
+{
+ return false;
+}
+#endif
diff --git a/arch/powerpc/include/asm/switch_to.h
b/arch/powerpc/include/asm/switch_to.h
index 5b03d8a82..537998997 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -44,10 +44,7 @@ extern void enable_kernel_altivec(void);
extern void flush_altivec_to_thread(struct task_struct *);
extern void giveup_altivec(struct task_struct *);
extern void save_altivec(struct task_struct *);
-static inline void disable_kernel_altivec(void)
-{
- msr_check_and_clear(MSR_VEC);
-}
+extern void disable_kernel_altivec(void);
#else
static inline void save_altivec(struct task_struct *t) { }
static inline void __giveup_altivec(struct task_struct *t) { }
@@ -56,10 +53,7 @@ static inline void __giveup_altivec(struct task_struct *t) {
}
#ifdef CONFIG_VSX
extern void enable_kernel_vsx(void);
extern void flush_vsx_to_thread(struct task_struct *);
-static inline void disable_kernel_vsx(void)
-{
- msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
-}
+extern void disable_kernel_vsx(void);
#endif
#ifdef CONFIG_SPE
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index e436d708a..41a0ab500 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -267,6 +267,29 @@ static int restore_fp(struct task_struct *tsk) { return 0;
}
#ifdef CONFIG_ALTIVEC
#define loadvec(thr) ((thr).load_vec)
+/*
+ * Track whether the kernel is using the SIMD state
+ * currently.
+ *
+ * This flag is used:
+ *
+ * - by IRQ context code to potentially use the FPU
+ * if it's unused.
+ *
+ * - to debug kernel_altivec/vsx_begin()/end() correctness
+ */
+static DEFINE_PER_CPU(bool, in_kernel_simd);
+
+static bool kernel_simd_disabled(void)
+{
+ return this_cpu_read(in_kernel_simd);
+}
+
+static bool interrupted_kernel_simd_idle(void)
+{
+ return !kernel_simd_disabled();
+}
+
static void __giveup_altivec(struct task_struct *tsk)
{
unsigned long msr;
@@ -295,7 +318,9 @@ void enable_kernel_altivec(void)
{
unsigned long cpumsr;
- WARN_ON(preemptible());
+ WARN_ON_ONCE(preemptible());
+ WARN_ON_ONCE(this_cpu_read(in_kernel_simd));
+ this_cpu_write(in_kernel_simd, true);
cpumsr = msr_check_and_set(MSR_VEC);
@@ -316,6 +341,14 @@ void enable_kernel_altivec(void)
}
EXPORT_SYMBOL(enable_kernel_altivec);
+extern void disable_kernel_altivec(void)
+{
+ WARN_ON_ONCE(!this_cpu_read(in_kernel_simd));
+ this_cpu_write(in_kernel_simd, false);
+ msr_check_and_clear(MSR_VEC);
+}
+EXPORT_SYMBOL(disable_kernel_altivec);
+
/*
* Make sure the VMX/Altivec register state in the
* the thread_struct is up to date for task tsk.
@@ -371,7 +404,8 @@ static bool interrupted_user_mode(void)
bool irq_simd_usable(void)
{
return !in_interrupt() ||
- interrupted_user_mode();
+ interrupted_user_mode() ||
+ interrupted_kernel_simd_idle();
}
EXPORT_SYMBOL(irq_simd_usable);
@@ -411,7 +445,9 @@ void enable_kernel_vsx(void)
{
unsigned long cpumsr;
- WARN_ON(preemptible());
+ WARN_ON_ONCE(preemptible());
+ WARN_ON_ONCE(this_cpu_read(in_kernel_simd));
+ this_cpu_write(in_kernel_simd, true);
cpumsr = msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
@@ -433,6 +469,14 @@ void enable_kernel_vsx(void)
}
EXPORT_SYMBOL(enable_kernel_vsx);
+void disable_kernel_vsx(void)
+{
+ WARN_ON_ONCE(!this_cpu_read(in_kernel_simd));
+ this_cpu_write(in_kernel_simd, false);
+ msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
+}
+EXPORT_SYMBOL(disable_kernel_vsx);
+
void flush_vsx_to_thread(struct task_struct *tsk)
{
if (tsk->thread.regs) {
--
2.21.0.1020.gf2820cf01a
