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Revert "clocksource: arch_timer: make virtual counter access configurable"

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This reverts commit dc9b4c45b2.
Disable userspace virtual counter access intended to makes it
difficult to obtain precise timing measurements of the cache
side channel. But it has been deprecated since it was found
to be ineffective.

Change-Id: I5cf59632ff1beb6ea51a53bea4eb3ad9467d4cd0
Signed-off-by: Maria Yu <aiquny@codeaurora.org>
This commit is contained in:
Maria Yu 2021-05-06 11:22:59 +08:00
commit 14ecafa9d5
2 changed files with 1 additions and 10 deletions
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8
drivers/clocksource/Kconfig
View file

@ -385,14 +385,6 @@ config SUN50I_ERRATUM_UNKNOWN1
the Allwinner A64 SoC. The workaround will only be active if the
allwinner,erratum-unknown1 property is found in the timer node.
config ARM_ARCH_TIMER_VCT_ACCESS
bool "Support for ARM architected timer virtual counter access in userspace"
default n
depends on ARM_ARCH_TIMER
help
This option enables support for reading the ARM architected timer's
virtual counter in userspace.
config ARM_GLOBAL_TIMER
bool "Support for the ARM global timer" if COMPILE_TEST
select TIMER_OF if OF

3
drivers/clocksource/arm_arch_timer.c
View file

@ -863,8 +863,7 @@ 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() ||
!IS_ENABLED(CONFIG_ARM_ARCH_TIMER_VCT_ACCESS))
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;