Re: [PATCH RESEND v2 2/2] virt: acrn: Make remove_cpu sysfs invisible with !CONFIG_HOTPLUG_CPU

[Shuo A Liu]

Hi,

On Tue 23.Feb'21 at 15:25:30 +0000, Qais Yousef wrote:
> On 02/21/21 21:43, shuo.a.liu@xxxxxxxxx wrote:
> > From: Shuo Liu <shuo.a.liu@xxxxxxxxx>
> >
> > Without cpu hotplug support, vCPU cannot be removed from a Service VM.
> > Don't expose remove_cpu sysfs when CONFIG_HOTPLUG_CPU disabled.
> >
> > Signed-off-by: Shuo Liu <shuo.a.liu@xxxxxxxxx>
> > Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # build-tested
> > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Qais Yousef <qais.yousef@xxxxxxx>
> > ---
> >  drivers/virt/acrn/hsm.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
> > index 1f6b7c54a1a4..6996ea6219e5 100644
> > --- a/drivers/virt/acrn/hsm.c
> > +++ b/drivers/virt/acrn/hsm.c
> > @@ -404,6 +404,14 @@ static ssize_t remove_cpu_store(struct device *dev,
> >  }
> >  static DEVICE_ATTR_WO(remove_cpu);
> >
> > +static umode_t acrn_attr_visible(struct kobject *kobj, struct attribute *a, int n)
> > +{
> > +       if (a == &dev_attr_remove_cpu.attr)
> > +               return IS_ENABLED(CONFIG_HOTPLUG_CPU) ? a->mode : 0;
> > +
> > +       return a->mode;
> > +}
> > +
>
> I can't find this code in Linus' master. But this looks fine from my narrow

Now, the code is still in linux-next tree only.

> PoV. Protecting the attribute with ifdef CONFIG_HOTPLUG_CPU is easier to read
> for me, but this doesn't mean this approach is not fine.

Just FYI, Greg prefers this solution.
https://lore.kernel.org/lkml/20210212045724.77846-1-shuo.a.liu@xxxxxxxxx/

Thanks
shuo