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Commit a86bd139 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled 



Userspace being allowed to use read CNTVCT_EL0 anytime (and not
only in the VDSO), we need to enable trapping whenever a cntvct
workaround is enabled on a given CPU.

Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent bee67c53

drivers/clocksource/arm_arch_timer.c

+32 −13
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ static enum ppi_nr arch_timer_uses_ppi = VIRT_PPI; 
static bool arch_timer_c3stop;

static bool arch_timer_mem_use_virtual;

static bool arch_counter_suspend_stop;

static bool vdso_default = true;



static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
@@ -383,6 +384,17 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa 
	}



	static_branch_enable(&arch_timer_read_ool_enabled);



	/*

	 * Don't use the vdso fastpath if errata require using the

	 * out-of-line counter accessor. We may change our mind pretty

	 * late in the game (with a per-CPU erratum, for example), so

	 * change both the default value and the vdso itself.

	 */

	if (wa->read_cntvct_el0) {

		clocksource_counter.archdata.vdso_direct = false;

		vdso_default = false;

	}

}



static void arch_timer_check_ool_workaround(enum arch_timer_erratum_match_type type,
@@ -443,11 +455,19 @@ static void arch_timer_check_ool_workaround(enum arch_timer_erratum_match_type t 
	__val;								\

})



static bool arch_timer_this_cpu_has_cntvct_wa(void)

{

	const struct arch_timer_erratum_workaround *wa;



	wa = __this_cpu_read(timer_unstable_counter_workaround);

	return wa && wa->read_cntvct_el0;

}

#else

#define arch_timer_check_ool_workaround(t,a)		do { } while(0)

#define erratum_set_next_event_tval_virt(...)		({BUG(); 0;})

#define erratum_set_next_event_tval_phys(...)		({BUG(); 0;})

#define erratum_handler(fn, r, ...)			({false;})

#define arch_timer_this_cpu_has_cntvct_wa()		({false;})

#endif /* CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND */



static __always_inline irqreturn_t timer_handler(const int access,
@@ -660,14 +680,22 @@ static void arch_counter_set_user_access(void) 
{

	u32 cntkctl = arch_timer_get_cntkctl();



	/* Disable user access to the timers and the physical counter */

	/* Disable user access to the timers and both counters */

	/* Also disable virtual event stream */

	cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN

			| ARCH_TIMER_USR_VT_ACCESS_EN

		        | ARCH_TIMER_USR_VCT_ACCESS_EN

			| ARCH_TIMER_VIRT_EVT_EN

			| ARCH_TIMER_USR_PCT_ACCESS_EN);



	/* Enable user access to the virtual counter */

	/*

	 * Enable user access to the virtual counter if it doesn't

	 * need to be workaround. The vdso may have been already

	 * disabled though.

	 */

	if (arch_timer_this_cpu_has_cntvct_wa())

		pr_info("CPU%d: Trapping CNTVCT access\n", smp_processor_id());

	else

		cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;



	arch_timer_set_cntkctl(cntkctl);
@@ -791,16 +819,7 @@ static void __init arch_counter_register(unsigned type) 
		else

			arch_timer_read_counter = arch_counter_get_cntpct;



		clocksource_counter.archdata.vdso_direct = true;



#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND

		/*

		 * Don't use the vdso fastpath if errata require using

		 * the out-of-line counter accessor.

		 */

		if (static_branch_unlikely(&arch_timer_read_ool_enabled))

			clocksource_counter.archdata.vdso_direct = false;

#endif

		clocksource_counter.archdata.vdso_direct = vdso_default;

	} else {

		arch_timer_read_counter = arch_counter_get_cntvct_mem;

	}