[PATCH 031/208] x86/fpu: Factor out the FPU bug detection code into fpu__init_check_bugs()

Ingo Molnar
2015-05-05T16:28:37Z

Move the boot-time FPU bug detection code to the other FPU boot time
init code in fpu/init.c.

No change in code size:

text data bss dec hex filename
13044568 1884440 1130496 16059504 f50c70 vmlinux.before
13044568 1884440 1130496 16059504 f50c70 vmlinux.after

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/i387.h | 1 +
arch/x86/kernel/cpu/bugs.c | 53 +----------------------------------------------------
arch/x86/kernel/fpu/init.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+), 52 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index c8ee395dd6c6..89ae3e051741 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -24,6 +24,7 @@ extern void fpu__flush_thread(struct task_struct *tsk);

extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
extern void fpu__restore(void);
+extern void fpu__init_check_bugs(void);

extern bool irq_fpu_usable(void);

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 03445346ee0a..eb8be0c5823b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -17,52 +17,6 @@
#include <asm/paravirt.h>
#include <asm/alternative.h>

-static double __initdata x = 4195835.0;
-static double __initdata y = 3145727.0;
-
-/*
- * This used to check for exceptions..
- * However, it turns out that to support that,
- * the XMM trap handlers basically had to
- * be buggy. So let's have a correct XMM trap
- * handler, and forget about printing out
- * some status at boot.
- *
- * We should really only care about bugs here
- * anyway. Not features.
- */
-static void __init check_fpu(void)
-{
- s32 fdiv_bug;
-
- kernel_fpu_begin();
-
- /*
- * trap_init() enabled FXSR and company _before_ testing for FP
- * problems here.
- *
- * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug
- */
- __asm__("fninit\n\t"
- "fldl %1\n\t"
- "fdivl %2\n\t"
- "fmull %2\n\t"
- "fldl %1\n\t"
- "fsubp %%st,%%st(1)\n\t"
- "fistpl %0\n\t"
- "fwait\n\t"
- "fninit"
- : "=m" (*&fdiv_bug)
- : "m" (*&x), "m" (*&y));
-
- kernel_fpu_end();
-
- if (fdiv_bug) {
- set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);
- pr_warn("Hmm, FPU with FDIV bug\n");
- }
-}
-
void __init check_bugs(void)
{
identify_boot_cpu();
@@ -85,10 +39,5 @@ void __init check_bugs(void)
'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
alternative_instructions();

- /*
- * kernel_fpu_begin/end() in check_fpu() relies on the patched
- * alternative instructions.
- */
- if (cpu_has_fpu)
- check_fpu();
+ fpu__init_check_bugs();
}
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 5e06aa6cc22e..4eabb426e910 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -4,6 +4,69 @@
#include <asm/fpu-internal.h>
#include <asm/tlbflush.h>

+/*
+ * Boot time CPU/FPU FDIV bug detection code:
+ */
+
+static double __initdata x = 4195835.0;
+static double __initdata y = 3145727.0;
+
+/*
+ * This used to check for exceptions..
+ * However, it turns out that to support that,
+ * the XMM trap handlers basically had to
+ * be buggy. So let's have a correct XMM trap
+ * handler, and forget about printing out
+ * some status at boot.
+ *
+ * We should really only care about bugs here
+ * anyway. Not features.
+ */
+static void __init check_fpu(void)
+{
+ s32 fdiv_bug;
+
+ kernel_fpu_begin();
+
+ /*
+ * trap_init() enabled FXSR and company _before_ testing for FP
+ * problems here.
+ *
+ * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug
+ */
+ __asm__("fninit\n\t"
+ "fldl %1\n\t"
+ "fdivl %2\n\t"
+ "fmull %2\n\t"
+ "fldl %1\n\t"
+ "fsubp %%st,%%st(1)\n\t"
+ "fistpl %0\n\t"
+ "fwait\n\t"
+ "fninit"
+ : "=m" (*&fdiv_bug)
+ : "m" (*&x), "m" (*&y));
+
+ kernel_fpu_end();
+
+ if (fdiv_bug) {
+ set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);
+ pr_warn("Hmm, FPU with FDIV bug\n");
+ }
+}
+
+void fpu__init_check_bugs(void)
+{
+ /*
+ * kernel_fpu_begin/end() in check_fpu() relies on the patched
+ * alternative instructions.
+ */
+ if (cpu_has_fpu)
+ check_fpu();
+}
+
+/*
+ * Boot time FPU feature detection code:
+ */
unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
EXPORT_SYMBOL_GPL(xstate_size);
--
2.1.0