Re: [RFC PATCH v2 2/2] tools/misc: Add xen-vcpus-stats tool

[Julien Grall <julien@xxxxxxx>]

Hi,

Sorry for the late reply.

On 17/03/2023 11:01, Matias Ezequiel Vara Larsen wrote:
> On Thu, Feb 23, 2023 at 08:31:29PM +0000, Julien Grall wrote:
> > > > +#define rmb()   asm volatile("lfence":::"memory")
> > > This is rmb(), but rmb() isn't what you want.
> > >
> > > You want smp_rmb(), which is
> > >
> > > #define smp_rmb() asm volatile ("" ::: "memory")
> >  From the generic PoV, I find smp_rmb() a bit misleading because it is not
> > clear in this context whether we are referring to the SMP-ness of the
> > hypervisor or the tools domain.
> >
> > If the latter, then technically it could be uniprocessor domain and one
> > could argue that for Arm it could be downgraded to just a compiler barrier.
> >
> > AFAICT, this would not be the case here because we are getting data from
> > Xen. So we always need a "dmb ish".
> >
> > So, I would suggest to name it virt_*() (to match Linux's naming).
> >
> > Also, is this tool meant to be arch-agnostic? If so, then we need to
> > introduce the proper barrier for the other arch.
> Thanks Julien for the comment. Is it `xen_rmb()` meant for that?
I believe so.

> Matias
--
Julien Grall