From a8e4c0a919ae310944ed2c9ace11cf3ccd8a609b Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 19 Jan 2018 15:42:09 +0000 Subject: [PATCH] arm64: Move BP hardening to check_and_switch_context 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 Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas --- arch/arm64/mm/context.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index ff99a880a730..301417ae2ba8 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -234,6 +234,9 @@ 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(); + /* * Defer TTBR0_EL1 setting for user threads to uaccess_enable() when * emulating PAN. @@ -249,8 +252,6 @@ 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) -- 2.11.0