:orphan:

.. title:: CONFIG_DISABLE_SSBD

.. kconfig:: CONFIG_DISABLE_SSBD

CONFIG_DISABLE_SSBD
###################

*Disable Speculative Store Bypass*

Type: ``bool``

Help
====

.. code-block:: none

    This option will disable Speculative Store Bypass in order to
    mitigate against certain kinds of side channel attacks.  Quoting
    the "Speculative Execution Side Channels" document, version 2.0:

        When SSBD is set, loads will not execute speculatively
        until the addresses of all older stores are known.  This
        ensure s that a load does not speculatively consume stale
        data values due to bypassing an older store on the same
        logical processor.

    If enabled, this applies to all threads in the system.

    Even if enabled, will have no effect on CPUs that do not
    require this feature.

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

\ :kconfig:`USERSPACE <CONFIG_USERSPACE>` && \ :kconfig:`X86 <CONFIG_X86>`

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

Default
=======

- y if !\ :kconfig:`X86_NO_SPECTRE_V4 <CONFIG_X86_NO_SPECTRE_V4>`

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



At ``<Zephyr Architecture>/x86/Kconfig:432``

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

Menu path: (Top) → X86 Architecture Options

.. code-block:: kconfig

    config DISABLE_SSBD
    	bool "Disable Speculative Store Bypass"
    	default y if !X86_NO_SPECTRE_V4
    	depends on USERSPACE && X86
    	help
    	  This option will disable Speculative Store Bypass in order to
    	  mitigate against certain kinds of side channel attacks.  Quoting
    	  the "Speculative Execution Side Channels" document, version 2.0:
	  
    	      When SSBD is set, loads will not execute speculatively
    	      until the addresses of all older stores are known.  This
    	      ensure s that a load does not speculatively consume stale
    	      data values due to bypassing an older store on the same
    	      logical processor.
	  
    	  If enabled, this applies to all threads in the system.
	  
    	  Even if enabled, will have no effect on CPUs that do not
    	  require this feature.

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