:orphan:

.. title:: CONFIG_LAZY_FPU_SHARING

.. kconfig:: CONFIG_LAZY_FPU_SHARING

CONFIG_LAZY_FPU_SHARING
#######################

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

Type: ``bool``

Help
====

.. code-block:: none

    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
===================

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

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

Default
=======

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

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



At ``<Architecture>/x86/core/Kconfig.ia32:121``

Included via ``Kconfig:8`` → ``Kconfig.zephyr:39`` → ``<Architecture>/Kconfig:12`` → ``<Architecture>/x86/Kconfig:482``

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

.. code-block:: kconfig

    config LAZY_FPU_SHARING
    	bool
    	default y if X86_NO_LAZY_FP || !USERSPACE
    	depends on FPU && !EAGER_FPU_SHARING && FPU_SHARING && CPU_HAS_FPU && !X86_64 && 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.)*