Adrian-Ken Rueegsegger 7ce8464b3a hw_x86_64: Enable FPU support ... * Enable the use of the FXSAVE and FXRSTOR instructions, see Intel SDM Vol. 3C, section 2.5. * The state of the x87 floating point unit (FPU) is loaded and saved on demand. * Make the cr0 control register accessible in the Cpu class. This is in preparation of the upcoming FPU management. * Access to the FPU is disabled by setting the Task Switch flag in the cr0 register. * Access to the FPU is enabled by clearing the Task Switch flag in the cr0 register. * Implement FPU initialization * Add is_fpu_enabled helper function * Add pointer to CPU lazy state to CPU class * Init FPU when finishing kernel initialization * Add function to retry FPU instruction: Similar to the ARM mechanism to retry undefined instructions, implement a function for retrying an FPU instruction. If a floating-point instruction causes an #NM exception due to the FPU being disabled, it can be retried after the correct FPU state is restored, saving the current state and enabling the FPU in the process. * Disable FPU when switching to different user context: This enables lazy save/restore of the FPU since trying to execute a floating point instruction when the FPU is disabled will cause a #NM exception. * Declare constant for #NM exception * Retry FPU instruction on #NM exception * Assure alignment of FXSAVE area: The FXSAVE area is 512-byte memory region that must be 16-byte aligned. As it turns out the alignment attribute is not honored in all cases so add a workaround to assure the alignment constraint is met by manually rounding the start of the FXSAVE area to the next 16-byte boundary if necessary.		2015-03-27 11:53:31 +01:00
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cpu_state.h	hw_x86_64: Enable FPU support	2015-03-27 11:53:31 +01:00