linux-kernel - RE: [PATCH] vdpa: Consider device id larger than 31

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Message-ID: <PH0PR12MB54813A22AA1240EE5EBEE48ADC669@PH0PR12MB5481.namprd12.prod.outlook.com>
Date:   Mon, 29 Nov 2021 07:22:45 +0000
From:   Parav Pandit <parav@...dia.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Eli Cohen <elic@...dia.com>
CC:     Jason Wang <jasowang@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        mst <mst@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
        "kbuild-all@...ts.01.org" <kbuild-all@...ts.01.org>,
        kernel test robot <lkp@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "kbuild@...ts.01.org" <kbuild@...ts.01.org>
Subject: RE: [PATCH] vdpa: Consider device id larger than 31



> From: Dan Carpenter <dan.carpenter@...cle.com>
> Sent: Monday, November 29, 2021 12:29 PM
> 
> On Sun, Nov 28, 2021 at 09:14:35AM +0200, Eli Cohen wrote:
> > On Fri, Nov 26, 2021 at 10:48:12AM +0800, Jason Wang wrote:
> > > On Fri, Nov 26, 2021 at 2:09 AM Parav Pandit <parav@...dia.com> wrote:
> > > >
> > > > virtio device id value can be more than 31. Hence, use BIT_ULL in
> > > > assignment.
> > > >
> > > > Fixes: 33b347503f01 ("vdpa: Define vdpa mgmt device, ops and a
> > > > netlink interface")
> > > > Reported-by: kernel test robot <lkp@...el.com>
> > > > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> > > > Signed-off-by: Parav Pandit <parav@...dia.com>
> > >
> > > Acked-by: Jason Wang <jasowang@...hat.com>
> > >
> > > > ---
> > > >  drivers/vdpa/vdpa.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index
> > > > 7332a74a4b00..e91c71aeeddf 100644
> > > > --- a/drivers/vdpa/vdpa.c
> > > > +++ b/drivers/vdpa/vdpa.c
> > > > @@ -404,7 +404,7 @@ static int vdpa_mgmtdev_fill(const struct
> vdpa_mgmt_dev *mdev, struct sk_buff *m
> > > >                 goto msg_err;
> > > >
> > > >         while (mdev->id_table[i].device) {
> > > > -               supported_classes |= BIT(mdev->id_table[i].device);
> > > > +               supported_classes |=
> > > > + BIT_ULL(mdev->id_table[i].device);
> > > >                 i++;
> > > >         }
> > > >
> >
> > type of mdev->id_table[i].device is __u32 so in theory you're limited
> > to device ID's up to 63.
> 
> A u32 can fit numbers up to 4 million?  These .device numbers are normally
> hardcoded defines listed in usr/include/linux/virtio_ids.h
> 
> But sometimes they're not like in vp_modern_probe() which does:
> 
> 	mdev->id.device = pci_dev->device - 0x1040;
> 
> I don't know if an assert is really worth it, considering how almost all of them
> are hardcoded.  Also if we do want an assert maybe there is a better place to
> put it?
I am changing above fix to report device id only upto 63.
Others higher values (which are not part of the current spec) will be ignored.
There is no need for assert for any undefined value anyway.