[ARM] 4111/1: Allow VFP to work with thread migration on SMP

The current lazy saving of the VFP registers is no longer possible
with thread migration on SMP. This patch implements a per-CPU
vfp-state pointer and the saving of the VFP registers at every context
switch. The registers restoring is still performed in a lazy way.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 26 insertions, 4 deletions

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 490d9d18a7d1..f1e5951dc721 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -28,7 +28,7 @@ void vfp_testing_entry(void);
 void vfp_support_entry(void);
 
 void (*vfp_vector)(void) = vfp_testing_entry;
-union vfp_state *last_VFP_context;
+union vfp_state *last_VFP_context[NR_CPUS];
 
 /*
  * Dual-use variable.
@@ -41,13 +41,35 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
 {
         struct thread_info *thread = v;
         union vfp_state *vfp;
+        __u32 cpu = thread->cpu;
 
         if (likely(cmd == THREAD_NOTIFY_SWITCH)) {
+                u32 fpexc = fmrx(FPEXC);
+
+#ifdef CONFIG_SMP
+                /*
+                 * On SMP, if VFP is enabled, save the old state in
+                 * case the thread migrates to a different CPU. The
+                 * restoring is done lazily.
+                 */
+                if ((fpexc & FPEXC_ENABLE) && last_VFP_context[cpu]) {
+                        vfp_save_state(last_VFP_context[cpu], fpexc);
+                        last_VFP_context[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)
+                        last_VFP_context[cpu] = NULL;
+#endif
+
                 /*
                  * Always disable VFP so we can lazily save/restore the
                  * old state.
                  */
-                fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE);
+                fmxr(FPEXC, fpexc & ~FPEXC_ENABLE);
                 return NOTIFY_DONE;
         }
 
@@ -68,8 +90,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
         }
 
         /* flush and release case: Per-thread VFP cleanup. */
-        if (last_VFP_context == vfp)
-                last_VFP_context = NULL;
+        if (last_VFP_context[cpu] == vfp)
+                last_VFP_context[cpu] = NULL;
 
         return NOTIFY_DONE;
 }