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x86/speculation: Split out TIF update 

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
This commit is contained in:
Thomas Gleixner 2018-11-25 19:33:51 +01:00
parent 46f7ecb1e7
commit e6da8bb6f9
1 changed files with 23 additions and 12 deletions
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35
arch/x86/kernel/cpu/bugs.c
View File

@ -702,10 +702,29 @@ static void ssb_select_mitigation(void)
#undef pr_fmt #undef pr_fmt
#define pr_fmt(fmt) "Speculation prctl: " 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; 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 && if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
ssb_mode != SPEC_STORE_BYPASS_SECCOMP) ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
return -ENXIO; return -ENXIO;
@ -716,28 +735,20 @@ static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
if (task_spec_ssb_force_disable(task)) if (task_spec_ssb_force_disable(task))
return -EPERM; return -EPERM;
task_clear_spec_ssb_disable(task); 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; break;
case PR_SPEC_DISABLE: case PR_SPEC_DISABLE:
task_set_spec_ssb_disable(task); 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; break;
case PR_SPEC_FORCE_DISABLE: case PR_SPEC_FORCE_DISABLE:
task_set_spec_ssb_disable(task); task_set_spec_ssb_disable(task);
task_set_spec_ssb_force_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; break;
default: default:
return -ERANGE; 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; return 0;
} }