On Fri, Dec 01, 2017 at 12:14:07PM -0800, Jakub Kicinski wrote:
> On Fri, 1 Dec 2017 14:43:06 +0100, Phil Sutter wrote:
> > On Thu, Nov 30, 2017 at 05:35:39PM -0800, Jakub Kicinski wrote:
> > [...]
> > > +static int nsim_vfs_enable(struct netdevsim *ns, unsigned int num_vfs)
> > > +{
> > > + ns->vfconfigs = kcalloc(num_vfs, sizeof(struct nsim_vf_config),
> > > + GFP_KERNEL);
> > > + if (!ns->vfconfigs)
> > > + return -ENOMEM;
> > > + ns->num_vfs = num_vfs;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static void nsim_vfs_disable(struct netdevsim *ns)
> > > +{
> > > + kfree(ns->vfconfigs);
> > > + ns->vfconfigs = NULL;
> > > + ns->num_vfs = 0;
> > > +}
> >
> > Why not something like:
> >
> > | static int nsim_vfs_set(struct netdevsim *ns, unsigned int num_vfs)
> > | {
> > | void *ptr = krealloc(ns->vfconfigs,
> > | num_vfs * sizeof(struct nsim_vf_config),
> > | GFP_KERNEL);
> > |
> > | if (!ptr)
> > | return -ENOMEM;
> > |
> > | ns->vfconfigs = ptr;
> > | ns->num_vfs = num_vfs;
> > | return 0;
> > | }
>
> Um. It either frees or allocates, never reallocates so I felt realloc
> is misleading. ZERO_SIZE_PTR is less clearly a NULL than a NULL. I
> will have to specify __GFP_ZERO. It's not a calloc so there could be
> potentially some overflows?
I don't understand: How can overflows happen if I use malloc() instead
of calloc()?
> > > +static ssize_t
> > > +nsim_numvfs_store(struct device *dev, struct device_attribute *attr,
> > > + const char *buf, size_t count)
> > > +{
> > > + struct netdevsim *ns = to_nsim(dev);
> > > + unsigned int num_vfs;
> > > + int ret;
> > > +
> > > + ret = kstrtouint(buf, 0, &num_vfs);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + rtnl_lock();
> > > + if (ns->num_vfs == num_vfs)
> > > + goto exit_good;
> >
> > Then replace this:
> >
> > > + if (ns->num_vfs && num_vfs) {
> > > + ret = -EBUSY;
> > > + goto exit_unlock;
> > > + }
> > > +
> > > + if (num_vfs) {
> > > + ret = nsim_vfs_enable(ns, num_vfs);
> > > + if (ret)
> > > + goto exit_unlock;
> > > + } else {
> > > + nsim_vfs_disable(ns);
> > > + }
> >
> > with just:
> >
> > | nsim_vfs_set(ns, num_vfs);
>
> I'm trying to mirror the PCI subsystem behaviour here, which only
> allows enable or disable, not increase. I felt we should follow how
> real devices behave:
>
> /* enable VFs */
> if (pdev->sriov->num_VFs) {
> dev_warn(&pdev->dev, "%d VFs already enabled. Disable before
> enabling %d VFs\n",
> pdev->sriov->num_VFs, num_vfs);
> return -EBUSY;
> }
>
> So IOW this is intentional.
Ah, I see. Yes, then it makes sense! Keeping this virtual VF
functionality as close to real ones as possible is certainly feasible.
> > > + ret = count;
> > > +exit_unlock:
> > > + rtnl_unlock();
> > > +
> > > + return ret;
> > > +}
> >
> > [...]
> >
> > > +static void nsim_free(struct net_device *dev)
> > > +{
> > > + struct netdevsim *ns = netdev_priv(dev);
> > > +
> > > + device_unregister(&ns->dev);
> > > }
> >
> > Shouldn't this also kfree(ns->vfconfigs)?
>
> It's in uninit, I will move it to release.
Oh, I missed that. If you're certain this won't lead to memleaks, no
objection from my side. :)
Cheers, Phil
