diff options
Diffstat (limited to 'Documentation/userspace-api/spec_ctrl.rst')
| -rw-r--r-- | Documentation/userspace-api/spec_ctrl.rst | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/Documentation/userspace-api/spec_ctrl.rst b/Documentation/userspace-api/spec_ctrl.rst index 5e8ed9eef9aa..61fe020b23a2 100644 --- a/Documentation/userspace-api/spec_ctrl.rst +++ b/Documentation/userspace-api/spec_ctrl.rst @@ -26,7 +26,8 @@ PR_GET_SPECULATION_CTRL PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature which is selected with arg2 of prctl(2). The return value uses bits 0-3 with -the following meaning: +the following meaning (with the caveat that PR_SPEC_L1D_FLUSH has less obvious +semantics, see documentation for that specific control below): ==== ====================== ================================================== Bit Define Description @@ -80,11 +81,15 @@ Value Meaning ERANGE arg3 is incorrect, i.e. it's neither PR_SPEC_ENABLE nor PR_SPEC_DISABLE nor PR_SPEC_FORCE_DISABLE. -ENXIO Control of the selected speculation misfeature is not possible. - See PR_GET_SPECULATION_CTRL. +ENXIO For PR_SPEC_STORE_BYPASS: control of the selected speculation misfeature + is not possible via prctl, because of the system's boot configuration. + +EPERM Speculation was disabled with PR_SPEC_FORCE_DISABLE and caller tried to + enable it again. + +EPERM For PR_SPEC_L1D_FLUSH and PR_SPEC_INDIRECT_BRANCH: control of the + mitigation is not possible because of the system's boot configuration. -EPERM Speculation was disabled with PR_SPEC_FORCE_DISABLE and caller - tried to enable it again. ======= ================================================================= Speculation misfeature controls @@ -110,6 +115,9 @@ Speculation misfeature controls - PR_SPEC_L1D_FLUSH: Flush L1D Cache on context switch out of the task (works only when tasks run on non SMT cores) +For this control, PR_SPEC_ENABLE means that the **mitigation** is enabled (L1D +is flushed), PR_SPEC_DISABLE means it is disabled. + Invocations: * prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_L1D_FLUSH, 0, 0, 0); * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_L1D_FLUSH, PR_SPEC_ENABLE, 0, 0); |