[GIT PULL] x86/fpu changes for v3.11

From: Ingo Molnar
Date: Mon Jul 01 2013 - 06:28:11 EST

Linus,

Please pull the latest x86-fpu-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-fpu-for-linus

HEAD: 5f8c4218148822fde6eebbeefc34bd0a6061e031 x86, fpu: Use static_cpu_has_safe before alternatives

There are two bigger changes in this tree:

- Add an [early-use-]safe static_cpu_has() variant and other robustness
improvements, including the new CONFIG_X86_DEBUG_STATIC_CPU_HAS=y
debugging facility, motivated by recent obscure FPU code bugs,
by Borislav Petkov

- Reimplement FPU detection code in C and drop the old asm code,
by H. Peter Anvin.

Thanks,

Ingo

------------------>
Borislav Petkov (4):
x86, cpu: Add a synthetic, always true, cpu feature
x86: Sanity-check static_cpu_has usage
x86: Add a static_cpu_has_safe variant
x86, fpu: Use static_cpu_has_safe before alternatives

H. Peter Anvin (1):
x86: Get rid of ->hard_math and all the FPU asm fu


arch/x86/Kconfig.debug | 10 +++
arch/x86/include/asm/cpufeature.h | 118 ++++++++++++++++++++++++++++++++++--
arch/x86/include/asm/fpu-internal.h | 4 +-
arch/x86/include/asm/processor.h | 3 +-
arch/x86/kernel/asm-offsets_32.c | 1 -
arch/x86/kernel/cpu/bugs.c | 21 +------
arch/x86/kernel/cpu/common.c | 19 +++++-
arch/x86/kernel/cpu/cyrix.c | 2 +-
arch/x86/kernel/cpu/proc.c | 4 +-
arch/x86/kernel/head_32.S | 21 -------
arch/x86/kernel/i387.c | 59 ++++++++++++++----
arch/x86/kernel/xsave.c | 5 +-
arch/x86/lguest/boot.c | 2 +-
arch/x86/xen/enlighten.c | 2 +-
14 files changed, 201 insertions(+), 70 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c198b7e..c6acdf7 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -304,4 +304,14 @@ config DEBUG_NMI_SELFTEST

If unsure, say N.

+config X86_DEBUG_STATIC_CPU_HAS
+ bool "Debug alternatives"
+ depends on DEBUG_KERNEL
+ ---help---
+ This option causes additional code to be generated which
+ fails if static_cpu_has() is used before alternatives have
+ run.
+
+ If unsure, say N.
+
endmenu
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index e99ac27..47538a6 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -92,7 +92,7 @@
#define X86_FEATURE_LFENCE_RDTSC (3*32+18) /* "" Lfence synchronizes RDTSC */
#define X86_FEATURE_11AP (3*32+19) /* "" Bad local APIC aka 11AP */
#define X86_FEATURE_NOPL (3*32+20) /* The NOPL (0F 1F) instructions */
- /* 21 available, was AMD_C1E */
+#define X86_FEATURE_ALWAYS (3*32+21) /* "" Always-present feature */
#define X86_FEATURE_XTOPOLOGY (3*32+22) /* cpu topology enum extensions */
#define X86_FEATURE_TSC_RELIABLE (3*32+23) /* TSC is known to be reliable */
#define X86_FEATURE_NONSTOP_TSC (3*32+24) /* TSC does not stop in C states */
@@ -356,15 +356,36 @@ extern const char * const x86_power_flags[32];
#endif /* CONFIG_X86_64 */

#if __GNUC__ >= 4
+extern void warn_pre_alternatives(void);
+extern bool __static_cpu_has_safe(u16 bit);
+
/*
* Static testing of CPU features. Used the same as boot_cpu_has().
* These are only valid after alternatives have run, but will statically
* patch the target code for additional performance.
- *
*/
static __always_inline __pure bool __static_cpu_has(u16 bit)
{
#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5
+
+#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS
+ /*
+ * Catch too early usage of this before alternatives
+ * have run.
+ */
+ asm goto("1: jmp %l[t_warn]\n"
+ "2:\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n"
+ " .long 0\n" /* no replacement */
+ " .word %P0\n" /* 1: do replace */
+ " .byte 2b - 1b\n" /* source len */
+ " .byte 0\n" /* replacement len */
+ ".previous\n"
+ /* skipping size check since replacement size = 0 */
+ : : "i" (X86_FEATURE_ALWAYS) : : t_warn);
+#endif
+
asm goto("1: jmp %l[t_no]\n"
"2:\n"
".section .altinstructions,\"a\"\n"
@@ -379,7 +400,13 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
return true;
t_no:
return false;
-#else
+
+#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS
+ t_warn:
+ warn_pre_alternatives();
+ return false;
+#endif
+#else /* GCC_VERSION >= 40500 */
u8 flag;
/* Open-coded due to __stringify() in ALTERNATIVE() */
asm volatile("1: movb $0,%0\n"
@@ -411,11 +438,94 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
__static_cpu_has(bit) : \
boot_cpu_has(bit) \
)
+
+static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
+{
+#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5
+/*
+ * We need to spell the jumps to the compiler because, depending on the offset,
+ * the replacement jump can be bigger than the original jump, and this we cannot
+ * have. Thus, we force the jump to the widest, 4-byte, signed relative
+ * offset even though the last would often fit in less bytes.
+ */
+ asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
+ "2:\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 3f - .\n" /* repl offset */
+ " .word %P1\n" /* always replace */
+ " .byte 2b - 1b\n" /* src len */
+ " .byte 4f - 3f\n" /* repl len */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "3: .byte 0xe9\n .long %l[t_no] - 2b\n"
+ "4:\n"
+ ".previous\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 0\n" /* no replacement */
+ " .word %P0\n" /* feature bit */
+ " .byte 2b - 1b\n" /* src len */
+ " .byte 0\n" /* repl len */
+ ".previous\n"
+ : : "i" (bit), "i" (X86_FEATURE_ALWAYS)
+ : : t_dynamic, t_no);
+ return true;
+ t_no:
+ return false;
+ t_dynamic:
+ return __static_cpu_has_safe(bit);
+#else /* GCC_VERSION >= 40500 */
+ u8 flag;
+ /* Open-coded due to __stringify() in ALTERNATIVE() */
+ asm volatile("1: movb $2,%0\n"
+ "2:\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 3f - .\n" /* repl offset */
+ " .word %P2\n" /* always replace */
+ " .byte 2b - 1b\n" /* source len */
+ " .byte 4f - 3f\n" /* replacement len */
+ ".previous\n"
+ ".section .discard,\"aw\",@progbits\n"
+ " .byte 0xff + (4f-3f) - (2b-1b)\n" /* size check */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "3: movb $0,%0\n"
+ "4:\n"
+ ".previous\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 5f - .\n" /* repl offset */
+ " .word %P1\n" /* feature bit */
+ " .byte 4b - 3b\n" /* src len */
+ " .byte 6f - 5f\n" /* repl len */
+ ".previous\n"
+ ".section .discard,\"aw\",@progbits\n"
+ " .byte 0xff + (6f-5f) - (4b-3b)\n" /* size check */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "5: movb $1,%0\n"
+ "6:\n"
+ ".previous\n"
+ : "=qm" (flag)
+ : "i" (bit), "i" (X86_FEATURE_ALWAYS));
+ return (flag == 2 ? __static_cpu_has_safe(bit) : flag);
+#endif
+}
+
+#define static_cpu_has_safe(bit) \
+( \
+ __builtin_constant_p(boot_cpu_has(bit)) ? \
+ boot_cpu_has(bit) : \
+ _static_cpu_has_safe(bit) \
+)
#else
/*
* gcc 3.x is too stupid to do the static test; fall back to dynamic.
*/
-#define static_cpu_has(bit) boot_cpu_has(bit)
+#define static_cpu_has(bit) boot_cpu_has(bit)
+#define static_cpu_has_safe(bit) boot_cpu_has(bit)
#endif

#define cpu_has_bug(c, bit) cpu_has(c, (bit))
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index e25cc33..4d0bda7 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

@@ -345,7 +343,7 @@ static inline void __thread_fpu_end(struct task_struct *tsk)

static inline void __thread_fpu_begin(struct task_struct *tsk)
{
- if (!use_eager_fpu())
+ if (!static_cpu_has_safe(X86_FEATURE_EAGER_FPU))
clts();
__thread_set_has_fpu(tsk);
}
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 22224b3..578f8b1 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 0ef4bba..d67c4be 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 4112be9..0344534 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 22018f7..a4a07c0 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);
@@ -724,6 +723,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)

if (this_cpu->c_bsp_init)
this_cpu->c_bsp_init(c);
+
+ setup_force_cpu_cap(X86_FEATURE_ALWAYS);
}

void __init early_cpu_init(void)
@@ -1363,3 +1364,17 @@ void __cpuinit cpu_init(void)
fpu_init();
}
#endif
+
+#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS
+void warn_pre_alternatives(void)
+{
+ WARN(1, "You're using static_cpu_has before alternatives have run!\n");
+}
+EXPORT_SYMBOL_GPL(warn_pre_alternatives);
+#endif
+
+inline bool __static_cpu_has_safe(u16 bit)
+{
+ return boot_cpu_has(bit);
+}
+EXPORT_SYMBOL_GPL(__static_cpu_has_safe);
diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c
index d048d5c..7582f47 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 37a198b..aee6317 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 73afd11..e65ddc6 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 cb33909..b627746 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 ada87a3..d6c28ac 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 7114c63..d482bca 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 a492be2..2fa02bc 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
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