From a86bd139f2ae02f960caeb0c1dd5f871d3e087cd Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Wed, 1 Feb 2017 12:07:15 +0000 Subject: [PATCH] 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: Thomas Gleixner Signed-off-by: Marc Zyngier --- drivers/clocksource/arm_arch_timer.c | 45 ++++++++++++++++++++-------- 1 file changed, 32 insertions(+), 13 deletions(-) diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 5c114da0ed71..f8adea258cf0 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -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, @@ -660,15 +680,23 @@ 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 */ - cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN; + /* + * 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; }