virt_vtimer_save is calculating the new time for the vtimer in: "v->arch.virt_timer.cval + v->domain->arch.virt_timer_base.offset - boot_count". In this formula, "cval + offset" might cause uint64_t overflow. Changing it to "ticks_to_ns(v->domain->arch.virt_timer_base.offset - boot_count) + ticks_to_ns(v->arch.virt_timer.cval)" can avoid overflow, and "ticks_to_ns(arch.virt_timer_base.offset - boot_count)" will be always the same, which has been caculated in domain_vtimer_init. Introduce a new field virt_timer_base.nanoseconds to store this value for arm in struct arch_domain, so we can use it directly.
Signed-off-by: Jiamei Xie <jiamei....@arm.com> Change-Id: Ib80cee51eaf844661e6f92154a0339ad2a652f9b --- was "xen/arm: avoid vtimer flip-flop transition in context switch". v3 changes: -re-write commit message -store nanoseconds in virt_timer_base instead of adding a new structure -assign to nanoseconds first, then seconds --- xen/arch/arm/include/asm/domain.h | 1 + xen/arch/arm/vtimer.c | 9 ++++++--- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/xen/arch/arm/include/asm/domain.h b/xen/arch/arm/include/asm/domain.h index ed63c2b6f9..cd9ce19b4b 100644 --- a/xen/arch/arm/include/asm/domain.h +++ b/xen/arch/arm/include/asm/domain.h @@ -71,6 +71,7 @@ struct arch_domain struct { uint64_t offset; + s_time_t nanoseconds; } virt_timer_base; struct vgic_dist vgic; diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c index 6b78fea77d..aeaea78e4c 100644 --- a/xen/arch/arm/vtimer.c +++ b/xen/arch/arm/vtimer.c @@ -63,7 +63,9 @@ static void virt_timer_expired(void *data) int domain_vtimer_init(struct domain *d, struct xen_arch_domainconfig *config) { d->arch.virt_timer_base.offset = get_cycles(); - d->time_offset.seconds = ticks_to_ns(d->arch.virt_timer_base.offset - boot_count); + d->arch.virt_timer_base.nanoseconds = + ticks_to_ns(d->arch.virt_timer_base.offset - boot_count); + d->time_offset.seconds = d->arch.virt_timer_base.nanoseconds; do_div(d->time_offset.seconds, 1000000000); config->clock_frequency = timer_dt_clock_frequency; @@ -144,8 +146,9 @@ void virt_timer_save(struct vcpu *v) if ( (v->arch.virt_timer.ctl & CNTx_CTL_ENABLE) && !(v->arch.virt_timer.ctl & CNTx_CTL_MASK)) { - set_timer(&v->arch.virt_timer.timer, ticks_to_ns(v->arch.virt_timer.cval + - v->domain->arch.virt_timer_base.offset - boot_count)); + set_timer(&v->arch.virt_timer.timer, + v->domain->arch.virt_timer_base.nanoseconds + + ticks_to_ns(v->arch.virt_timer.cval)); } } -- 2.25.1