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, 46 insertions, 34 deletions

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 8f8102d967b..baf632b221d 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -8,6 +8,7 @@
 #include <linux/module.h>
 #include <linux/regset.h>
 #include <linux/sched.h>
+#include <linux/bootmem.h>
 
 #include <asm/sigcontext.h>
 #include <asm/processor.h>
@@ -35,17 +36,18 @@
 #endif
 
 static unsigned int		mxcsr_feature_mask __read_mostly = 0xffffffffu;
+unsigned int xstate_size;
+static struct i387_fxsave_struct fx_scratch __cpuinitdata;
 
-void mxcsr_feature_mask_init(void)
+void __cpuinit mxcsr_feature_mask_init(void)
 {
 	unsigned long mask = 0;
 
 	clts();
 	if (cpu_has_fxsr) {
-		memset(&current->thread.i387.fxsave, 0,
-		       sizeof(struct i387_fxsave_struct));
-		asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
-		mask = current->thread.i387.fxsave.mxcsr_mask;
+		memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
+		asm volatile("fxsave %0" : : "m" (fx_scratch));
+		mask = fx_scratch.mxcsr_mask;
 		if (mask == 0)
 			mask = 0x0000ffbf;
 	}
@@ -53,6 +55,17 @@ void mxcsr_feature_mask_init(void)
 	stts();
 }
 
+void __init init_thread_xstate(void)
+{
+	if (cpu_has_fxsr)
+		xstate_size = sizeof(struct i387_fxsave_struct);
+#ifdef CONFIG_X86_32
+	else
+		xstate_size = sizeof(struct i387_fsave_struct);
+#endif
+	init_task.thread.xstate = alloc_bootmem(xstate_size);
+}
+
 #ifdef CONFIG_X86_64
 /*
  * Called at bootup to set up the initial FPU state that is later cloned
@@ -61,10 +74,6 @@ void mxcsr_feature_mask_init(void)
 void __cpuinit fpu_init(void)
 {
 	unsigned long oldcr0 = read_cr0();
-	extern void __bad_fxsave_alignment(void);
-
-	if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
-		__bad_fxsave_alignment();
 
 	set_in_cr4(X86_CR4_OSFXSR);
 	set_in_cr4(X86_CR4_OSXMMEXCPT);
@@ -93,18 +102,19 @@ void init_fpu(struct task_struct *tsk)
 	}
 
 	if (cpu_has_fxsr) {
-		memset(&tsk->thread.i387.fxsave, 0,
-		       sizeof(struct i387_fxsave_struct));
-		tsk->thread.i387.fxsave.cwd = 0x37f;
+		struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
+
+		memset(fx, 0, xstate_size);
+		fx->cwd = 0x37f;
 		if (cpu_has_xmm)
-			tsk->thread.i387.fxsave.mxcsr = MXCSR_DEFAULT;
+			fx->mxcsr = MXCSR_DEFAULT;
 	} else {
-		memset(&tsk->thread.i387.fsave, 0,
-		       sizeof(struct i387_fsave_struct));
-		tsk->thread.i387.fsave.cwd = 0xffff037fu;
-		tsk->thread.i387.fsave.swd = 0xffff0000u;
-		tsk->thread.i387.fsave.twd = 0xffffffffu;
-		tsk->thread.i387.fsave.fos = 0xffff0000u;
+		struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
+		memset(fp, 0, xstate_size);
+		fp->cwd = 0xffff037fu;
+		fp->swd = 0xffff0000u;
+		fp->twd = 0xffffffffu;
+		fp->fos = 0xffff0000u;
 	}
 	/*
 	 * Only the device not available exception or ptrace can call init_fpu.
@@ -132,7 +142,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 	init_fpu(target);
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-				   &target->thread.i387.fxsave, 0, -1);
+				   &target->thread.xstate->fxsave, 0, -1);
 }
 
 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
@@ -148,12 +158,12 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 	set_stopped_child_used_math(target);
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-				 &target->thread.i387.fxsave, 0, -1);
+				 &target->thread.xstate->fxsave, 0, -1);
 
 	/*
 	 * mxcsr reserved bits must be masked to zero for security reasons.
 	 */
-	target->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
+	target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 
 	return ret;
 }
@@ -233,7 +243,7 @@ static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 static void
 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 {
-	struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
+	struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 	struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;
@@ -273,7 +283,7 @@ static void convert_to_fxsr(struct task_struct *tsk,
 			    const struct user_i387_ia32_struct *env)
 
 {
-	struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
+	struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 	struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;
@@ -310,7 +320,8 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 
 	if (!cpu_has_fxsr) {
 		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-					   &target->thread.i387.fsave, 0, -1);
+					   &target->thread.xstate->fsave, 0,
+					   -1);
 	}
 
 	if (kbuf && pos == 0 && count == sizeof(env)) {
@@ -338,7 +349,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 
 	if (!cpu_has_fxsr) {
 		return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-					  &target->thread.i387.fsave, 0, -1);
+					  &target->thread.xstate->fsave, 0, -1);
 	}
 
 	if (pos > 0 || count < sizeof(env))
@@ -358,11 +369,11 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 {
 	struct task_struct *tsk = current;
+	struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 
 	unlazy_fpu(tsk);
-	tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
-	if (__copy_to_user(buf, &tsk->thread.i387.fsave,
-			   sizeof(struct i387_fsave_struct)))
+	fp->status = fp->swd;
+	if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
 		return -1;
 	return 1;
 }
@@ -370,6 +381,7 @@ static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 {
 	struct task_struct *tsk = current;
+	struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 	struct user_i387_ia32_struct env;
 	int err = 0;
 
@@ -379,12 +391,12 @@ static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 	if (__copy_to_user(buf, &env, sizeof(env)))
 		return -1;
 
-	err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
+	err |= __put_user(fx->swd, &buf->status);
 	err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 	if (err)
 		return -1;
 
-	if (__copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
+	if (__copy_to_user(&buf->_fxsr_env[0], fx,
 			   sizeof(struct i387_fxsave_struct)))
 		return -1;
 	return 1;
@@ -417,7 +429,7 @@ static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
 	struct task_struct *tsk = current;
 
 	clear_fpu(tsk);
-	return __copy_from_user(&tsk->thread.i387.fsave, buf,
+	return __copy_from_user(&tsk->thread.xstate->fsave, buf,
 				sizeof(struct i387_fsave_struct));
 }
 
@@ -428,10 +440,10 @@ static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
 	int err;
 
 	clear_fpu(tsk);
-	err = __copy_from_user(&tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
+	err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
 			       sizeof(struct i387_fxsave_struct));
 	/* mxcsr reserved bits must be masked to zero for security reasons */
-	tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
+	tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 	if (err || __copy_from_user(&env, buf, sizeof(env)))
 		return 1;
 	convert_to_fxsr(tsk, &env);