diff options
| author | Marc Zyngier <maz@kernel.org> | 2026-02-26 08:22:32 +0000 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-04 07:20:56 -0500 |
| commit | 594d85ce95d2c2fc90fbfa81ff66876ce7c3a2df (patch) | |
| tree | 3fda196944d5b5cde26f037071c2b72de0d632f8 | |
| parent | 409fe5e265bf23cdf6d9cc24f93cb561dc6527d2 (diff) | |
arm64: Fix sampling the "stable" virtual counter in preemptible section
[ Upstream commit e5cb94ba5f96d691d8885175d4696d6ae6bc5ec9 ]
Ben reports that when running with CONFIG_DEBUG_PREEMPT, using
__arch_counter_get_cntvct_stable() results in well deserves warnings,
as we access a per-CPU variable without preemption disabled.
Fix the issue by disabling preemption on reading the counter. We can
probably do a lot better by not disabling preemption on systems that
do not require horrible workarounds to return a valid counter value,
but this plugs the issue for the time being.
Fixes: 29cc0f3aa7c6 ("arm64: Force the use of CNTVCT_EL0 in __delay()")
Reported-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/aZw3EGs4rbQvbAzV@e134344.arm.com
Tested-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: André Draszik <andre.draszik@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | arch/arm64/lib/delay.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm64/lib/delay.c b/arch/arm64/lib/delay.c index 2b6041cc8448..15a953ac6f0f 100644 --- a/arch/arm64/lib/delay.c +++ b/arch/arm64/lib/delay.c @@ -32,7 +32,11 @@ static inline unsigned long xloops_to_cycles(unsigned long xloops) * Note that userspace cannot change the offset behind our back either, * as the vcpu mutex is held as long as KVM_RUN is in progress. */ -#define __delay_cycles() __arch_counter_get_cntvct_stable() +static cycles_t notrace __delay_cycles(void) +{ + guard(preempt_notrace)(); + return __arch_counter_get_cntvct_stable(); +} void __delay(unsigned long cycles) { |