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94 lines
2.0 KiB
C
94 lines
2.0 KiB
C
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/*
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* x86 FPU boot time init code
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*/
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#include <asm/fpu-internal.h>
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#include <asm/tlbflush.h>
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unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
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unsigned int xstate_size;
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EXPORT_SYMBOL_GPL(xstate_size);
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static struct i387_fxsave_struct fx_scratch;
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static void mxcsr_feature_mask_init(void)
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{
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unsigned long mask = 0;
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if (cpu_has_fxsr) {
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memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
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asm volatile("fxsave %0" : "+m" (fx_scratch));
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mask = fx_scratch.mxcsr_mask;
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if (mask == 0)
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mask = 0x0000ffbf;
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}
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mxcsr_feature_mask &= mask;
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}
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static void fpstate_xstate_init_size(void)
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{
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/*
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* Note that xstate_size might be overwriten later during
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* xsave_init().
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*/
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if (!cpu_has_fpu) {
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/*
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* Disable xsave as we do not support it if i387
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* emulation is enabled.
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*/
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setup_clear_cpu_cap(X86_FEATURE_XSAVE);
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setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
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xstate_size = sizeof(struct i387_soft_struct);
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return;
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}
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if (cpu_has_fxsr)
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xstate_size = sizeof(struct i387_fxsave_struct);
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else
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xstate_size = sizeof(struct i387_fsave_struct);
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}
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/*
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* Called on the boot CPU at bootup to set up the initial FPU state that
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* is later cloned into all processes.
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*
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* Also called on secondary CPUs to set up the FPU state of their
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* idle threads.
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*/
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void fpu__cpu_init(void)
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{
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unsigned long cr0;
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unsigned long cr4_mask = 0;
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#ifndef CONFIG_MATH_EMULATION
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if (!cpu_has_fpu) {
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pr_emerg("No FPU found and no math emulation present\n");
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pr_emerg("Giving up\n");
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for (;;)
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asm volatile("hlt");
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}
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#endif
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if (cpu_has_fxsr)
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cr4_mask |= X86_CR4_OSFXSR;
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if (cpu_has_xmm)
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cr4_mask |= X86_CR4_OSXMMEXCPT;
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if (cr4_mask)
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cr4_set_bits(cr4_mask);
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cr0 = read_cr0();
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cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
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if (!cpu_has_fpu)
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cr0 |= X86_CR0_EM;
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write_cr0(cr0);
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/*
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* fpstate_xstate_init_size() is only called once, to avoid overriding
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* 'xstate_size' during (secondary CPU) bootup or during CPU hotplug.
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*/
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if (xstate_size == 0)
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fpstate_xstate_init_size();
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mxcsr_feature_mask_init();
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xsave_init();
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eager_fpu_init();
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}
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