When a task is set for updating TIF_SPEC_IB throuth SECCOMP by others
and it's scheduled in the first time, a stale TIF_SPEC_IB value is
picked in cond_ibpb(). This is due to TIF_SPEC_IB is updated later at
__switch_to_xtra().
Add an extra call to speculation_ctrl_update_tif() to update it before
IBPB barrier.
Signed-off-by: Zhenzhong Duan <zhenzhong.d...@oracle.com>
---
arch/x86/include/asm/spec-ctrl.h | 1 +
arch/x86/kernel/process.c | 2 +-
arch/x86/mm/tlb.c | 4 +++-
3 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/spec-ctrl.h b/arch/x86/include/asm/spec-ctrl.h
index 5393bab..8b2814a 100644
--- a/arch/x86/include/asm/spec-ctrl.h
+++ b/arch/x86/include/asm/spec-ctrl.h
@@ -82,6 +82,7 @@ static inline u64 ssbd_tif_to_amd_ls_cfg(u64 tifn)
static inline void speculative_store_bypass_ht_init(void) { }
#endif
+extern unsigned long speculation_ctrl_update_tif(struct task_struct *tsk);
extern void speculation_ctrl_update(unsigned long tif);
extern void speculation_ctrl_update_current(void);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 90ae0ca..454e71d 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -446,7 +446,7 @@ static __always_inline void
__speculation_ctrl_update(unsigned long tifp,
wrmsrl(MSR_IA32_SPEC_CTRL, msr);
}
-static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
+unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
{
if (test_and_clear_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE)) {
if (task_spec_ssb_disable(tsk))
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 999d6d8..c0f3fcf 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -8,6 +8,7 @@
#include <linux/cpu.h>
#include <linux/debugfs.h>
+#include <asm/spec-ctrl.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/nospec-branch.h>
@@ -190,7 +191,8 @@ static void sync_current_stack_to_mm(struct mm_struct *mm)
static inline unsigned long mm_mangle_tif_spec_ib(struct task_struct *next)
{
- unsigned long next_tif = task_thread_info(next)->flags;
+ /* Update the flag bits to newest value actively */
+ unsigned long next_tif = speculation_ctrl_update_tif(next);
unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_IBPB;
return (unsigned long)next->mm | ibpb;
--
1.8.3.1
