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From: Jason Wang <jasowang@redhat.com>
Date: Tue, 16 Apr 2024 15:22:20 +0800
Message-ID: <CACGkMEth+QErT8dh_Oh+fz+wO6scLbRDUTkx86XDK7kX1uNCGg@mail.gmail.com>
Subject: Re: [PATCH] vDPA: fix incorrect VDPA_ATTR_MAX value
To: kovalev@altlinux.org
Cc: mst@redhat.com, parav@nvidia.com, edumazet@google.com, elic@nvidia.com, 
	linux-kernel@vger.kernel.org
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On Tue, Apr 16, 2024 at 3:18=E2=80=AFPM Jason Wang <jasowang@redhat.com> wr=
ote:
>
> On Tue, Apr 16, 2024 at 12:39=E2=80=AFAM <kovalev@altlinux.org> wrote:
> >
> > From: Vasiliy Kovalev <kovalev@altlinux.org>
> >
> > The VDPA_ATTR_MAX value should correspond to the index of the last
> > available member of the structure, not their total number.
>
> I think it's too late to change. More below.
>
> >
> > Otherwise, it can lead to interpretation errors in other functions
> > when the structure (.maxattr =3D VDPA_ATTR_MAX) member is actually
> > incremented by one and refers to invalid data.
> >
> > Fixes: 33b347503f01 ("vdpa: Define vdpa mgmt device, ops and a netlink =
interface")
> > Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
> > ---
> >  include/uapi/linux/vdpa.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> > index 43c51698195ceb..ab132a09565232 100644
> > --- a/include/uapi/linux/vdpa.h
> > +++ b/include/uapi/linux/vdpa.h
> > @@ -74,7 +74,8 @@ enum vdpa_attr {
> >         VDPA_ATTR_DEV_BLK_CFG_FLUSH,            /* u8 */
> >
> >         /* new attributes must be added above here */
> > -       VDPA_ATTR_MAX,
> > +       __VDPA_ATTR_MAX,
> > +       VDPA_ATTR_MAX   =3D __VDPA_ATTR_MAX - 1,
>
> Having a MAX in uapi is problematic as it may confuse the userspace. I
> think the correct way is to drop it from uAPI.

Too late to drop as well probably ...

Thanks

>
> Thanks
>
> >  };
> >
> >  #endif
> > --
> > 2.33.8
> >
> >