:orphan:

.. title:: DISABLE_SSBD

.. option:: CONFIG_DISABLE_SSBD

*Disable Speculative Store Bypass*

Type: ``bool``

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.

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

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

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

Default
=======

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

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

.. highlight:: kconfig

At ``arch/x86/Kconfig:269``

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

Menu path: (Top) → X86 Architecture Options

.. parsed-literal::

    config DISABLE_SSBD
    	bool "Disable Speculative Store Bypass"
    	default y if !\ :option:`X86_NO_SPECTRE_V4 <CONFIG_X86_NO_SPECTRE_V4>`
    	depends on \ :option:`USERSPACE <CONFIG_USERSPACE>` && \ :option:`X86 <CONFIG_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.)*