Re: [PATCH v3] xen/arm: avoid overflow when setting vtimer in context switch

[Julien Grall <julien@xxxxxxx>]

On 30/06/2022 06:20, Jiamei Xie wrote:
> Hi,
Hi Jiamei,

> > -----Original Message-----
> > From: Jiamei Xie <jiamei.xie@xxxxxxx>
> > Sent: 2022年6月30日 9:54
> > To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: Jiamei Xie <Jiamei.Xie@xxxxxxx>; Stefano Stabellini
> > <sstabellini@xxxxxxxxxx>; Julien Grall <julien@xxxxxxx>; Bertrand Marquis
> > <Bertrand.Marquis@xxxxxxx>; Volodymyr Babchuk
> > <Volodymyr_Babchuk@xxxxxxxx>; Wei Chen <Wei.Chen@xxxxxxx>
> > 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.xie@xxxxxxx>
> > Change-Id: Ib80cee51eaf844661e6f92154a0339ad2a652f9b
> I am sorry I forget to remove the Change-Id.
No worries. This can be dropped on commit (if no other changes are 
requested).
Cheers,

--
Julien Grall