ARM: vfp ptrace: no point flushing hw context for PTRACE_GETVFPREGS

If we're only reading the VFP context via the ptrace call, there's
no need to invalidate the hardware context - we only need to do that
on PTRACE_SETVFPREGS.  This allows more efficient monitoring of a
traced task.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 23 insertions, 2 deletions

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 86a57aeeda4a..def19f83d812 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -430,7 +430,11 @@ static inline void vfp_pm_init(void) { }
  * saved one. This function is used by the ptrace mechanism.
  */
 #ifdef CONFIG_SMP
-void vfp_sync_state(struct thread_info *thread)
+void vfp_sync_hwstate(struct thread_info *thread)
+{
+}
+
+void vfp_flush_hwstate(struct thread_info *thread)
 {
         /*
          * On SMP systems, the VFP state is automatically saved at every
@@ -441,7 +445,7 @@ void vfp_sync_state(struct thread_info *thread)
         thread->vfpstate.hard.cpu = NR_CPUS;
 }
 #else
-void vfp_sync_state(struct thread_info *thread)
+void vfp_sync_hwstate(struct thread_info *thread)
 {
         unsigned int cpu = get_cpu();
 
@@ -457,6 +461,23 @@ void vfp_sync_state(struct thread_info *thread)
                  */
                 fmxr(FPEXC, fpexc | FPEXC_EN);
                 vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
+                fmxr(FPEXC, fpexc);
+        }
+
+        put_cpu();
+}
+
+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 (last_VFP_context[cpu] == &thread->vfpstate) {
+                u32 fpexc = fmrx(FPEXC);
+
                 fmxr(FPEXC, fpexc & ~FPEXC_EN);
 
                 /*