4.19-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
commit e6da8bb6f9abb2628381904b24163c770e630bac upstream
The update of the TIF_SSBD flag and the conditional speculation control MSR update is done in the ssb_prctl_set() function directly. The upcoming prctl support for controlling indirect branch speculation via STIBP needs the same mechanism.
Split the code out and make it reusable. Reword the comment about updates for other tasks.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jkosina@suse.cz Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Dave Hansen dave.hansen@intel.com Cc: Casey Schaufler casey.schaufler@intel.com Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Waiman Long longman9394@gmail.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Dave Stewart david.c.stewart@intel.com Cc: Kees Cook keescook@chromium.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.652305076@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/bugs.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -700,10 +700,29 @@ static void ssb_select_mitigation(void) #undef pr_fmt #define pr_fmt(fmt) "Speculation prctl: " fmt
-static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) +static void task_update_spec_tif(struct task_struct *tsk, int tifbit, bool on) { bool update;
+ if (on) + update = !test_and_set_tsk_thread_flag(tsk, tifbit); + else + update = test_and_clear_tsk_thread_flag(tsk, tifbit); + + /* + * Immediately update the speculation control MSRs for the current + * task, but for a non-current task delay setting the CPU + * mitigation until it is scheduled next. + * + * This can only happen for SECCOMP mitigation. For PRCTL it's + * always the current task. + */ + if (tsk == current && update) + speculation_ctrl_update_current(); +} + +static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) +{ if (ssb_mode != SPEC_STORE_BYPASS_PRCTL && ssb_mode != SPEC_STORE_BYPASS_SECCOMP) return -ENXIO; @@ -714,28 +733,20 @@ static int ssb_prctl_set(struct task_str if (task_spec_ssb_force_disable(task)) return -EPERM; task_clear_spec_ssb_disable(task); - update = test_and_clear_tsk_thread_flag(task, TIF_SSBD); + task_update_spec_tif(task, TIF_SSBD, false); break; case PR_SPEC_DISABLE: task_set_spec_ssb_disable(task); - update = !test_and_set_tsk_thread_flag(task, TIF_SSBD); + task_update_spec_tif(task, TIF_SSBD, true); break; case PR_SPEC_FORCE_DISABLE: task_set_spec_ssb_disable(task); task_set_spec_ssb_force_disable(task); - update = !test_and_set_tsk_thread_flag(task, TIF_SSBD); + task_update_spec_tif(task, TIF_SSBD, true); break; default: return -ERANGE; } - - /* - * If being set on non-current task, delay setting the CPU - * mitigation until it is next scheduled. - */ - if (task == current && update) - speculation_ctrl_update_current(); - return 0; }