arm64: arch_timer: Disable CNTVCT_EL0 trap if workaround is enabled

hulk inclusion
category: performance
bugzilla: 16082
CVE: NA

-------------------------------------------------

It costs very much time to read CNTVCT_EL0, if a cntvct workaround
and CNTVCT_EL0 trap is enabled. To decrease the read time, we disable
CNTVCT_EL0 trap and do the cntvct workaround in the VDSO by adding
vdso_fix.
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/include/asm/clocksource.h

@@ -4,6 +4,7 @@
 
 struct arch_clocksource_data {
 	bool vdso_direct;	/* Usable for direct VDSO access? */
+	bool vdso_fix;		/* Need avoid the clock bug in VDSO? */
 };
 
 #endif

arch/arm64/include/asm/vdso_datapage.h

@@ -38,6 +38,7 @@ struct vdso_data {
 	__u32 tz_minuteswest;	/* Whacky timezone stuff */
 	__u32 tz_dsttime;
 	__u32 use_syscall;
+	__u32 vdso_fix;		/* Avoid the clock bug in VDSO */
 };
 
 #endif /* !__ASSEMBLY__ */

arch/arm64/kernel/vdso.c

@@ -224,6 +224,7 @@ void update_vsyscall(struct timekeeper *tk)
 	smp_wmb();
 
 	vdso_data->use_syscall			= use_syscall;
+	vdso_data->vdso_fix			= tk->tkr_mono.clock->archdata.vdso_fix;
 	vdso_data->xtime_coarse_sec		= tk->xtime_sec;
 	vdso_data->xtime_coarse_nsec		= tk->tkr_mono.xtime_nsec >>
 							tk->tkr_mono.shift;

drivers/clocksource/arm_arch_timer.c

@@ -76,6 +76,7 @@ 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 vdso_fix = false;
 
 static cpumask_t evtstrm_available = CPU_MASK_NONE;
 static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
@@ -550,8 +551,10 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
 	 * change both the default value and the vdso itself.
 	 */
 	if (wa->read_cntvct_el0) {
-		clocksource_counter.archdata.vdso_direct = false;
-		vdso_default = false;
+		clocksource_counter.archdata.vdso_direct = true;
+		clocksource_counter.archdata.vdso_fix = true;
+		vdso_default = true;
+		vdso_fix = true;
 	}
 }
 
@@ -855,7 +858,7 @@ static void arch_counter_set_user_access(void)
 	 * need to be workaround. The vdso may have been already
 	 * disabled though.
 	 */
-	if (arch_timer_this_cpu_has_cntvct_wa())
+	if (arch_timer_this_cpu_has_cntvct_wa() && !vdso_fix)
 		pr_info("CPU%d: Trapping CNTVCT access\n", smp_processor_id());
 	else
 		cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;
@@ -990,6 +993,7 @@ static void __init arch_counter_register(unsigned type)
 			arch_timer_read_counter = arch_counter_get_cntpct;
 
 		clocksource_counter.archdata.vdso_direct = vdso_default;
+		clocksource_counter.archdata.vdso_fix = vdso_fix;
 	} else {
 		arch_timer_read_counter = arch_counter_get_cntvct_mem;
 	}