x86: deduplicate the spectre_v2_user documentation

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 <aarcange@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201105001406.13005-2-aarcange@redhat.com

diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 19b897cb1d45ec8fb7a059772bb9f5750971d2fd..ab7d402c16779305343505251c6b547fdd1afa90 100644 (file)
--- 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
 --------------------------