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>

12 files changed, 60 insertions, 65 deletions

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index e25cc33ec54d..fb808d71cd70 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/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
 
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 22224b3b43bb..578f8b1d6910 100644
--- a/arch/x86/include/asm/processor.h
+++ b/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);
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 0ef4bba2acb7..d67c4be3e8b1 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/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);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4112be9a4659..03445346ee0a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/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();
 }
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 22018f70a671..d4dd99350e9d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/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);
diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c
index d048d5ca43c1..7582f475b163 100644
--- a/arch/x86/kernel/cpu/cyrix.c
+++ b/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 */
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 37a198bd48c8..aee6317b902f 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/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");
 }
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 73afd11799ca..e65ddc62e113 100644
--- a/arch/x86/kernel/head_32.S
+++ b/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"
 
 /*
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index cb339097b9ea..b627746f6b1a 100644
--- a/arch/x86/kernel/i387.c
+++ b/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() */
+}
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index ada87a329edc..d6c28acdf99c 100644
--- a/arch/x86/kernel/xsave.c
+++ b/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;
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 7114c63f047d..d482bcaf61c1 100644
--- a/arch/x86/lguest/boot.c
+++ b/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
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index a492be2635ac..2fa02bc50034 100644
--- a/arch/x86/xen/enlighten.c
+++ b/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