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hw_x86_64: Explicitly initialize MXCSR

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The assures that the MXCSR is initialized to the recommended value.
This commit is contained in:
Adrian-Ken Rueegsegger 2015-04-23 13:54:34 +02:00 committed by Christian Helmuth
parent ded302c61c
commit f2fe0eccb8
1 changed files with 28 additions and 3 deletions
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31
repos/base-hw/src/core/include/spec/x86/cpu_support.h
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@ -59,6 +59,10 @@ class Genode::Cpu_lazy_state
private:
enum {
MXCSR_DEFAULT = 0x1f80
};
/**
* FXSAVE area providing storage for x87 FPU, MMX, XMM, and MXCSR
* registers.
@ -91,10 +95,31 @@ class Genode::Cpu_lazy_state
inline void save() { asm volatile ("fxsave %0" : "=m" (*start)); }
/**
* Initialize FPU without checking for pending unmasked floating-point
* exceptions.
* Return current value of MXCSR register.
*/
inline void init() { asm volatile ("fninit"); };
static inline unsigned get_mxcsr()
{
unsigned value;
asm volatile ("stmxcsr %0" : "=m" (value));
return value;
}
/**
* Set MXCSR register to given value.
*/
static inline void set_mxcsr(unsigned value)
{
asm volatile ("ldmxcsr %0" : : "m" (value));
}
/**
* Initialize FPU without checking for pending unmasked floating-point
* exceptions and explicitly setting the MXCSR to the default value.
*/
inline void init() {
asm volatile ("fninit");
set_mxcsr(MXCSR_DEFAULT);
};
/**
* Set 16-byte aligned start of fxsave area.