:orphan:

.. title:: LAZY_FPU_SHARING

.. option:: CONFIG_LAZY_FPU_SHARING

*(No prompt -- not directly user assignable.)*

Type: ``bool``

Help
====

This hidden option allows multiple threads to use the floating point
registers, using logic to lazily save/restore the floating point
register state on context switch.

On Intel Core processors, may be vulnerable to exploits which allows
malware to read the contents of all floating point registers, see
CVE-2018-3665.

Direct dependencies
===================

\ :option:`FPU <CONFIG_FPU>` && !\ :option:`EAGER_FPU_SHARING <CONFIG_EAGER_FPU_SHARING>` && \ :option:`FPU_SHARING <CONFIG_FPU_SHARING>` && \ :option:`CPU_HAS_FPU <CONFIG_CPU_HAS_FPU>` && !\ :option:`X86_64 <CONFIG_X86_64>` && \ :option:`X86 <CONFIG_X86>`

*(Includes any dependencies from ifs and menus.)*

Default
=======

- y if \ :option:`X86_NO_LAZY_FP <CONFIG_X86_NO_LAZY_FP>` || !\ :option:`USERSPACE <CONFIG_USERSPACE>`

Kconfig definition
==================

.. highlight:: kconfig

At ``arch/x86/core/Kconfig.ia32:127``

Included via ``Kconfig:8`` → ``Kconfig.zephyr:29`` → ``arch/Kconfig:12`` → ``arch/x86/Kconfig:319``

Menu path: (Top) → X86 Architecture Options → Processor Capabilities → Architecture Floating Point Options

.. parsed-literal::

    config LAZY_FPU_SHARING
    	bool
    	default y if \ :option:`X86_NO_LAZY_FP <CONFIG_X86_NO_LAZY_FP>` || !\ :option:`USERSPACE <CONFIG_USERSPACE>`
    	depends on \ :option:`FPU <CONFIG_FPU>` && !\ :option:`EAGER_FPU_SHARING <CONFIG_EAGER_FPU_SHARING>` && \ :option:`FPU_SHARING <CONFIG_FPU_SHARING>` && \ :option:`CPU_HAS_FPU <CONFIG_CPU_HAS_FPU>` && !\ :option:`X86_64 <CONFIG_X86_64>` && \ :option:`X86 <CONFIG_X86>`
    	help
    	  This hidden option allows multiple threads to use the floating point
    	  registers, using logic to lazily save/restore the floating point
    	  register state on context switch.
	  
    	  On Intel Core processors, may be vulnerable to exploits which allows
    	  malware to read the contents of all floating point registers, see
    	  CVE-2018-3665.

*(The 'depends on' condition includes propagated dependencies from ifs and menus.)*