x86: Get rid of ->hard_math and all the FPU asm fu

Reimplement FPU detection code in C and drop old, not-so-recommended
detection method in asm. Move all the relevant stuff into i387.c where
it conceptually belongs. Finally drop cpuinfo_x86.hard_math.

[ hpa: huge thanks to Borislav for taking my original concept patch
  and productizing it ]

[ Boris, note to self: do not use static_cpu_has before alternatives! ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1367244262-29511-2-git-send-email-bp@alien8.de
Link: http://lkml.kernel.org/r/1365436666-9837-2-git-send-email-bp@alien8.de
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/fpu-internal.h

@@ -62,10 +62,8 @@ extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
 #define xstateregs_active	fpregs_active
 
 #ifdef CONFIG_MATH_EMULATION
-# define HAVE_HWFP		(boot_cpu_data.hard_math)
 extern void finit_soft_fpu(struct i387_soft_struct *soft);
 #else
-# define HAVE_HWFP		1
 static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
 #endif
 

arch/x86/include/asm/processor.h

@@ -89,9 +89,9 @@ struct cpuinfo_x86 {
 	char			wp_works_ok;	/* It doesn't on 386's */
 
 	/* Problems on some 486Dx4's and old 386's: */
-	char			hard_math;
 	char			rfu;
 	char			pad0;
+	char			pad1;
 #else
 	/* Number of 4K pages in DTLB/ITLB combined(in pages): */
 	int			x86_tlbsize;
@@ -164,6 +164,7 @@ extern const struct seq_operations cpuinfo_op;
 #define cache_line_size()	(boot_cpu_data.x86_cache_alignment)
 
 extern void cpu_detect(struct cpuinfo_x86 *c);
+extern void __cpuinit fpu_detect(struct cpuinfo_x86 *c);
 
 extern void early_cpu_init(void);
 extern void identify_boot_cpu(void);

arch/x86/kernel/asm-offsets_32.c

@@ -28,7 +28,6 @@ void foo(void)
 	OFFSET(CPUINFO_x86_vendor, cpuinfo_x86, x86_vendor);
 	OFFSET(CPUINFO_x86_model, cpuinfo_x86, x86_model);
 	OFFSET(CPUINFO_x86_mask, cpuinfo_x86, x86_mask);
-	OFFSET(CPUINFO_hard_math, cpuinfo_x86, hard_math);
 	OFFSET(CPUINFO_cpuid_level, cpuinfo_x86, cpuid_level);
 	OFFSET(CPUINFO_x86_capability, cpuinfo_x86, x86_capability);
 	OFFSET(CPUINFO_x86_vendor_id, cpuinfo_x86, x86_vendor_id);

arch/x86/kernel/cpu/bugs.c

@@ -17,15 +17,6 @@
 #include <asm/paravirt.h>
 #include <asm/alternative.h>
 
-static int __init no_387(char *s)
-{
-	boot_cpu_data.hard_math = 0;
-	write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
-	return 1;
-}
-
-__setup("no387", no_387);
-
 static double __initdata x = 4195835.0;
 static double __initdata y = 3145727.0;
 
@@ -44,15 +35,6 @@ static void __init check_fpu(void)
 {
 	s32 fdiv_bug;
 
-	if (!boot_cpu_data.hard_math) {
-#ifndef CONFIG_MATH_EMULATION
-		pr_emerg("No coprocessor found and no math emulation present\n");
-		pr_emerg("Giving up\n");
-		for (;;) ;
-#endif
-		return;
-	}
-
 	kernel_fpu_begin();
 
 	/*
@@ -107,5 +89,6 @@ void __init check_bugs(void)
 	 * kernel_fpu_begin/end() in check_fpu() relies on the patched
 	 * alternative instructions.
 	 */
-	check_fpu();
+	if (cpu_has_fpu)
+		check_fpu();
 }

arch/x86/kernel/cpu/common.c

@@ -711,10 +711,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		return;
 
 	cpu_detect(c);
-
 	get_cpu_vendor(c);
-
 	get_cpu_cap(c);
+	fpu_detect(c);
 
 	if (this_cpu->c_early_init)
 		this_cpu->c_early_init(c);

arch/x86/kernel/cpu/cyrix.c

@@ -333,7 +333,7 @@ static void __cpuinit init_cyrix(struct cpuinfo_x86 *c)
 		switch (dir0_lsn) {
 		case 0xd:  /* either a 486SLC or DLC w/o DEVID */
 			dir0_msn = 0;
-			p = Cx486_name[(c->hard_math) ? 1 : 0];
+			p = Cx486_name[(cpu_has_fpu ? 1 : 0)];
 			break;
 
 		case 0xe:  /* a 486S A step */

arch/x86/kernel/cpu/proc.c

@@ -37,8 +37,8 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
 		   static_cpu_has_bug(X86_BUG_FDIV) ? "yes" : "no",
 		   static_cpu_has_bug(X86_BUG_F00F) ? "yes" : "no",
 		   static_cpu_has_bug(X86_BUG_COMA) ? "yes" : "no",
-		   c->hard_math ? "yes" : "no",
-		   c->hard_math ? "yes" : "no",
+		   static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no",
+		   static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no",
 		   c->cpuid_level,
 		   c->wp_works_ok ? "yes" : "no");
 }

arch/x86/kernel/head_32.S

@@ -444,7 +444,6 @@ is486:
 	orl %ecx,%eax
 	movl %eax,%cr0
 
-	call check_x87
 	lgdt early_gdt_descr
 	lidt idt_descr
 	ljmp $(__KERNEL_CS),$1f
@@ -467,26 +466,6 @@ is486:
 	pushl $0		# fake return address for unwinder
 	jmp *(initial_code)
 
-/*
- * We depend on ET to be correct. This checks for 287/387.
- */
-check_x87:
-	movb $0,X86_HARD_MATH
-	clts
-	fninit
-	fstsw %ax
-	cmpb $0,%al
-	je 1f
-	movl %cr0,%eax		/* no coprocessor: have to set bits */
-	xorl $4,%eax		/* set EM */
-	movl %eax,%cr0
-	ret
-	ALIGN
-1:	movb $1,X86_HARD_MATH
-	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */
-	ret
-
-	
 #include "verify_cpu.S"
 
 /*

arch/x86/kernel/i387.c

@@ -131,7 +131,7 @@ static void __cpuinit init_thread_xstate(void)
 	 * xsave_init().
 	 */
 
-	if (!HAVE_HWFP) {
+	if (!cpu_has_fpu) {
 		/*
 		 * Disable xsave as we do not support it if i387
 		 * emulation is enabled.
@@ -158,6 +158,14 @@ void __cpuinit fpu_init(void)
 	unsigned long cr0;
 	unsigned long cr4_mask = 0;
 
+#ifndef CONFIG_MATH_EMULATION
+	if (!cpu_has_fpu) {
+		pr_emerg("No FPU found and no math emulation present\n");
+		pr_emerg("Giving up\n");
+		for (;;)
+			asm volatile("hlt");
+	}
+#endif
 	if (cpu_has_fxsr)
 		cr4_mask |= X86_CR4_OSFXSR;
 	if (cpu_has_xmm)
@@ -167,7 +175,7 @@ void __cpuinit fpu_init(void)
 
 	cr0 = read_cr0();
 	cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
-	if (!HAVE_HWFP)
+	if (!cpu_has_fpu)
 		cr0 |= X86_CR0_EM;
 	write_cr0(cr0);
 
@@ -185,7 +193,7 @@ void __cpuinit fpu_init(void)
 
 void fpu_finit(struct fpu *fpu)
 {
-	if (!HAVE_HWFP) {
+	if (!cpu_has_fpu) {
 		finit_soft_fpu(&fpu->state->soft);
 		return;
 	}
@@ -214,7 +222,7 @@ int init_fpu(struct task_struct *tsk)
 	int ret;
 
 	if (tsk_used_math(tsk)) {
-		if (HAVE_HWFP && tsk == current)
+		if (cpu_has_fpu && tsk == current)
 			unlazy_fpu(tsk);
 		tsk->thread.fpu.last_cpu = ~0;
 		return 0;
@@ -511,14 +519,13 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 	if (ret)
 		return ret;
 
-	if (!HAVE_HWFP)
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 
-	if (!cpu_has_fxsr) {
+	if (!cpu_has_fxsr)
 		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 					   &target->thread.fpu.state->fsave, 0,
 					   -1);
-	}
 
 	sanitize_i387_state(target);
 
@@ -545,13 +552,13 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 
 	sanitize_i387_state(target);
 
-	if (!HAVE_HWFP)
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 
-	if (!cpu_has_fxsr) {
+	if (!cpu_has_fxsr)
 		return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-					  &target->thread.fpu.state->fsave, 0, -1);
-	}
+					  &target->thread.fpu.state->fsave, 0,
+					  -1);
 
 	if (pos > 0 || count < sizeof(env))
 		convert_from_fxsr(&env, target);
@@ -592,3 +599,33 @@ int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 EXPORT_SYMBOL(dump_fpu);
 
 #endif	/* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
+
+static int __init no_387(char *s)
+{
+	setup_clear_cpu_cap(X86_FEATURE_FPU);
+	return 1;
+}
+
+__setup("no387", no_387);
+
+void __cpuinit fpu_detect(struct cpuinfo_x86 *c)
+{
+	unsigned long cr0;
+	u16 fsw, fcw;
+
+	fsw = fcw = 0xffff;
+
+	cr0 = read_cr0();
+	cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
+	write_cr0(cr0);
+
+	asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
+		     : "+m" (fsw), "+m" (fcw));
+
+	if (fsw == 0 && (fcw & 0x103f) == 0x003f)
+		set_cpu_cap(c, X86_FEATURE_FPU);
+	else
+		clear_cpu_cap(c, X86_FEATURE_FPU);
+
+	/* The final cr0 value is set in fpu_init() */
+}

arch/x86/kernel/xsave.c

@@ -243,7 +243,7 @@ int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 	if (!access_ok(VERIFY_WRITE, buf, size))
 		return -EACCES;
 
-	if (!HAVE_HWFP)
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_get(current, NULL, 0,
 			sizeof(struct user_i387_ia32_struct), NULL,
 			(struct _fpstate_ia32 __user *) buf) ? -1 : 1;
@@ -350,11 +350,10 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 	if (!used_math() && init_fpu(tsk))
 		return -1;
 
-	if (!HAVE_HWFP) {
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_set(current, NULL,
 				       0, sizeof(struct user_i387_ia32_struct),
 				       NULL, buf) != 0;
-	}
 
 	if (use_xsave()) {
 		struct _fpx_sw_bytes fx_sw_user;

arch/x86/lguest/boot.c

@@ -1410,7 +1410,7 @@ __init void lguest_init(void)
 	new_cpu_data.x86_capability[0] = cpuid_edx(1);
 
 	/* Math is always hard! */
-	new_cpu_data.hard_math = 1;
+	set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU);
 
 	/* We don't have features.  We have puppies!  Puppies! */
 #ifdef CONFIG_X86_MCE

arch/x86/xen/enlighten.c

@@ -1557,7 +1557,7 @@ asmlinkage void __init xen_start_kernel(void)
 #ifdef CONFIG_X86_32
 	/* set up basic CPUID stuff */
 	cpu_detect(&new_cpu_data);
-	new_cpu_data.hard_math = 1;
+	set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU);
 	new_cpu_data.wp_works_ok = 1;
 	new_cpu_data.x86_capability[0] = cpuid_edx(1);
 #endif