[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>
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 490d9d1..f1e5951 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -28,7 +28,7 @@
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 @@
{
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 @@
}
/* 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;
}