Hi,
> -----Original Message-----
> From: Jiamei Xie <jiamei....@arm.com>
> Sent: 2022年6月30日 9:54
> To: xen-devel@lists.xenproject.org
> Cc: Jiamei Xie <jiamei....@arm.com>; Stefano Stabellini
> <sstabell...@kernel.org>; Julien Grall <jul...@xen.org>; Bertrand Marquis
> <bertrand.marq...@arm.com>; Volodymyr Babchuk
> <volodymyr_babc...@epam.com>; Wei Chen <wei.c...@arm.com>
> Subject: [PATCH v3] xen/arm: avoid overflow when setting vtimer in context
> switch
>
> 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
I am sorry I forget to remove the Change-Id.
> ---
> 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
