Re: [PATCH v2 3/4] arm64: mte: Enable async tag check fault

On 1/14/21 2:25 PM, Catalin Marinas wrote:

On Thu, Jan 14, 2021 at 10:24:25AM +0000, Vincenzo Frascino wrote:

quoted

On 1/13/21 6:11 PM, Catalin Marinas wrote:

quoted

On Thu, Jan 07, 2021 at 05:29:07PM +0000, Vincenzo Frascino wrote:

quoted

 static inline void mte_sync_tags(pte_t *ptep, pte_t pte)
 {
 }

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 5346953e4382..74b020ce72d7 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c

@@ -37,6 +37,8 @@ static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	rcu_irq_enter_check_tick();
 	trace_hardirqs_off_finish();
+
+	mte_check_tfsr_el1();
 }
 
 /*

@@ -47,6 +49,8 @@ static void noinstr exit_to_kernel_mode(struct pt_regs *regs)
 {
 	lockdep_assert_irqs_disabled();
 
+	mte_check_tfsr_el1();
+
 	if (interrupts_enabled(regs)) {
 		if (regs->exit_rcu) {
 			trace_hardirqs_on_prepare();

@@ -243,6 +247,8 @@ asmlinkage void noinstr enter_from_user_mode(void)
 
 asmlinkage void noinstr exit_to_user_mode(void)
 {
+	mte_check_tfsr_el1();

While for kernel entry the asynchronous faults are sync'ed automatically
with TFSR_EL1, we don't have this for exit, so we'd need an explicit
DSB. But rather than placing it here, it's better if we add a bool sync
argument to mte_check_tfsr_el1() which issues a dsb() before checking
the register. I think that's the only place where such argument would be
true (for now).

Good point, I will add the dsb() in mte_check_tfsr_el1() but instead of a bool
parameter I will add something more explicit.

Or rename the function to mte_check_tfsr_el1_no_sync() and have a static
inline mte_check_tfsr_el1() which issues a dsb() before calling the
*no_sync variant.

Adding an enum instead here is not worth it (if that's what you meant by
not using a bool).

I like this option more, thanks for pointing it out.

-- 
Regards,
Vincenzo

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