From: Marc Zyngier <marc.zyngier@xxxxxxx> commit a8e4c0a919ae310944ed2c9ace11cf3ccd8a609b upstream. We call arm64_apply_bp_hardening() from post_ttbr_update_workaround, which has the unexpected consequence of being triggered on every exception return to userspace when ARM64_SW_TTBR0_PAN is selected, even if no context switch actually occured. This is a bit suboptimal, and it would be more logical to only invalidate the branch predictor when we actually switch to a different mm. In order to solve this, move the call to arm64_apply_bp_hardening() into check_and_switch_context(), where we're guaranteed to pick a different mm context. Acked-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> --- arch/arm64/mm/context.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index be42bd3dca5c..de5afc27b4e6 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -183,6 +183,8 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); switch_mm_fastpath: + arm64_apply_bp_hardening(); + cpu_switch_mm(mm->pgd, mm); } @@ -193,8 +195,6 @@ asmlinkage void post_ttbr_update_workaround(void) "ic iallu; dsb nsh; isb", ARM64_WORKAROUND_CAVIUM_27456, CONFIG_CAVIUM_ERRATUM_27456)); - - arm64_apply_bp_hardening(); } static int asids_init(void) -- 2.21.0.rc0.269.g1a574e7a288b
