Re: [PATCH net-next v3 05/18] net/smc: reserve CHID range for SMC-D virtual device

[Wen Gu]

On 2023/9/22 07:32, Wenjia Zhang wrote:
> On 21.09.23 15:19, Wen Gu wrote:
> > This patch reserve CHID range from 0xFF00 to 0xFFFF for SMC-D virtual
> > device and introduces helpers to identify them.
> >
> > Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
> > ---
> >   net/smc/smc_ism.h | 15 +++++++++++++++
> >   1 file changed, 15 insertions(+)
> >
> > diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
> > index 14d2e77..2ecc8de 100644
> > --- a/net/smc/smc_ism.h
> > +++ b/net/smc/smc_ism.h
> > @@ -15,6 +15,9 @@
> >   #include "smc.h"
> > +#define SMC_VIRT_ISM_CHID_MAX        0xFFFF
> > +#define SMC_VIRT_ISM_CHID_MIN        0xFF00
> > +
> >   struct smcd_dev_list {    /* List of SMCD devices */
> >       struct list_head list;
> >       struct mutex mutex;    /* Protects list of devices */
> > @@ -57,4 +60,16 @@ static inline int smc_ism_write(struct smcd_dev *smcd, u64 dmb_tok,
> >       return rc < 0 ? rc : 0;
> >   }
> > +static inline bool __smc_ism_is_virtdev(u16 chid)
> > +{
> > +    return (chid >= SMC_VIRT_ISM_CHID_MIN && chid <= SMC_VIRT_ISM_CHID_MAX);
> > +}
> > +
> > +static inline bool smc_ism_is_virtdev(struct smcd_dev *smcd)
> > +{
> > +    u16 chid = smcd->ops->get_chid(smcd);
> > +
> > +    return __smc_ism_is_virtdev(chid);
> > +}
> > +
> I'm wondering if barrier is needed here.

I think this helper doesn't involve memory race or multi-threaded/multi-processor
cases that needs enforcing ordering and synchronization of memory operations.

So IMHO barrier is no very necessary here.

Thank you.

> >   #endif