This would need updating to make prctl be the new default, but it's
simpler to delete it and refer to the dup.
Signed-off-by: Andrea Arcangeli <[email protected]>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 51 +------------------
1 file changed, 2 insertions(+), 49 deletions(-)
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 19b897cb1d45..ab7d402c1677 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -593,61 +593,14 @@ kernel command line.
Not specifying this option is equivalent to
spectre_v2=auto.
-For user space mitigation:
-
- spectre_v2_user=
-
- [X86] Control mitigation of Spectre variant 2
- (indirect branch speculation) vulnerability between
- user space tasks
-
- on
- Unconditionally enable mitigations. Is
- enforced by spectre_v2=on
-
- off
- Unconditionally disable mitigations. Is
- enforced by spectre_v2=off
-
- prctl
- Indirect branch speculation is enabled,
- but mitigation can be enabled via prctl
- per thread. The mitigation control state
- is inherited on fork.
-
- prctl,ibpb
- Like "prctl" above, but only STIBP is
- controlled per thread. IBPB is issued
- always when switching between different user
- space processes.
-
- seccomp
- Same as "prctl" above, but all seccomp
- threads will enable the mitigation unless
- they explicitly opt out.
-
- seccomp,ibpb
- Like "seccomp" above, but only STIBP is
- controlled per thread. IBPB is issued
- always when switching between different
- user space processes.
-
- auto
- Kernel selects the mitigation depending on
- the available CPU features and vulnerability.
-
- Default mitigation:
- If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
-
- Not specifying this option is equivalent to
- spectre_v2_user=auto.
-
In general the kernel by default selects
reasonable mitigations for the current CPU. To
disable Spectre variant 2 mitigations, boot with
spectre_v2=off. Spectre variant 1 mitigations
cannot be disabled.
+For spectre_v2_user see :doc:`/admin-guide/kernel-parameters`.
+
Mitigation selection guide
--------------------------
On Wed, Nov 04, 2020 at 07:14:06PM -0500, Andrea Arcangeli wrote:
> This would need updating to make prctl be the new default, but it's
> simpler to delete it and refer to the dup.
>
> Signed-off-by: Andrea Arcangeli <[email protected]>
I'll take this too.
-Kees
> ---
> Documentation/admin-guide/hw-vuln/spectre.rst | 51 +------------------
> 1 file changed, 2 insertions(+), 49 deletions(-)
>
> diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
> index 19b897cb1d45..ab7d402c1677 100644
> --- a/Documentation/admin-guide/hw-vuln/spectre.rst
> +++ b/Documentation/admin-guide/hw-vuln/spectre.rst
> @@ -593,61 +593,14 @@ kernel command line.
> Not specifying this option is equivalent to
> spectre_v2=auto.
>
> -For user space mitigation:
> -
> - spectre_v2_user=
> -
> - [X86] Control mitigation of Spectre variant 2
> - (indirect branch speculation) vulnerability between
> - user space tasks
> -
> - on
> - Unconditionally enable mitigations. Is
> - enforced by spectre_v2=on
> -
> - off
> - Unconditionally disable mitigations. Is
> - enforced by spectre_v2=off
> -
> - prctl
> - Indirect branch speculation is enabled,
> - but mitigation can be enabled via prctl
> - per thread. The mitigation control state
> - is inherited on fork.
> -
> - prctl,ibpb
> - Like "prctl" above, but only STIBP is
> - controlled per thread. IBPB is issued
> - always when switching between different user
> - space processes.
> -
> - seccomp
> - Same as "prctl" above, but all seccomp
> - threads will enable the mitigation unless
> - they explicitly opt out.
> -
> - seccomp,ibpb
> - Like "seccomp" above, but only STIBP is
> - controlled per thread. IBPB is issued
> - always when switching between different
> - user space processes.
> -
> - auto
> - Kernel selects the mitigation depending on
> - the available CPU features and vulnerability.
> -
> - Default mitigation:
> - If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
> -
> - Not specifying this option is equivalent to
> - spectre_v2_user=auto.
> -
> In general the kernel by default selects
> reasonable mitigations for the current CPU. To
> disable Spectre variant 2 mitigations, boot with
> spectre_v2=off. Spectre variant 1 mitigations
> cannot be disabled.
>
> +For spectre_v2_user see :doc:`/admin-guide/kernel-parameters`.
> +
> Mitigation selection guide
> --------------------------
>
>
--
Kees Cook