[PATCH 6.12 022/265] s390/vtime: Fix virtual timer forwarding

Greg Kroah-Hartman
2026-03-12T20:12:31Z

From: Heiko Carstens <hca@linux.ibm.com>

[ Upstream commit dbc0fb35679ed5d0adecf7d02137ac2c77244b3b ]

Since delayed accounting of system time [1] the virtual timer is
forwarded by do_account_vtime() but also vtime_account_kernel(),
vtime_account_softirq(), and vtime_account_hardirq(). This leads
to double accounting of system, guest, softirq, and hardirq time.

Remove accounting from the vtime_account*() family to restore old behavior.

There is only one user of the vtimer interface, which might explain
why nobody noticed this so far.

Fixes: b7394a5f4ce9 ("sched/cputime, s390: Implement delayed accounting of system time") [1]
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/vtime.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 234a0ba305108..122d30b104401 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -225,10 +225,6 @@ static u64 vtime_delta(void)
return timer - lc->last_update_timer;
}

-/*
- * Update process times based on virtual cpu times stored by entry.S
- * to the lowcore fields user_timer, system_timer & steal_clock.
- */
void vtime_account_kernel(struct task_struct *tsk)
{
struct lowcore *lc = get_lowcore();
@@ -238,27 +234,17 @@ void vtime_account_kernel(struct task_struct *tsk)
lc->guest_timer += delta;
else
lc->system_timer += delta;
-
- virt_timer_forward(delta);
}
EXPORT_SYMBOL_GPL(vtime_account_kernel);

void vtime_account_softirq(struct task_struct *tsk)
{
- u64 delta = vtime_delta();
-
- get_lowcore()->softirq_timer += delta;
-
- virt_timer_forward(delta);
+ get_lowcore()->softirq_timer += vtime_delta();
}

void vtime_account_hardirq(struct task_struct *tsk)
{
- u64 delta = vtime_delta();
-
- get_lowcore()->hardirq_timer += delta;
-
- virt_timer_forward(delta);
+ get_lowcore()->hardirq_timer += vtime_delta();
}

/*
--
2.51.0