x86, fpu: split FPU state from task struct - v5

Split the FPU save area from the task struct. This allows easy migration
of FPU context, and it's generally cleaner. It also allows the following
two optimizations:

1) only allocate when the application actually uses FPU, so in the first
lazy FPU trap. This could save memory for non-fpu using apps. Next patch
does this lazy allocation.

2) allocate the right size for the actual cpu rather than 512 bytes always.
Patches enabling xsave/xrstor support (coming shortly) will take advantage
of this.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
new file mode 100644
index 000000000000..ead24efbcba0
--- /dev/null
+++ b/arch/x86/kernel/process.c
@@ -0,0 +1,35 @@
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+
+static struct kmem_cache *task_xstate_cachep;
+
+int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
+{
+        *dst = *src;
+        dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
+        if (!dst->thread.xstate)
+                return -ENOMEM;
+        WARN_ON((unsigned long)dst->thread.xstate & 15);
+        memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
+        return 0;
+}
+
+void free_thread_info(struct thread_info *ti)
+{
+        kmem_cache_free(task_xstate_cachep, ti->task->thread.xstate);
+        ti->task->thread.xstate = NULL;
+
+        free_pages((unsigned long)(ti), get_order(THREAD_SIZE));
+}
+
+void arch_task_cache_init(void)
+{
+        task_xstate_cachep =
+                kmem_cache_create("task_xstate", xstate_size,
+                                  __alignof__(union thread_xstate),
+                                  SLAB_PANIC, NULL);
+}