linux-kernel - Re: [PATCH v2] Drivers: vmbus: Check for channel allocation before looking up relids

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Message-ID: <CAG-HVq-Knhdgwh4QCJ1U_N+bWYavguQ0axmx-TNgF+aCYoS2AA@mail.gmail.com>
Date:   Fri, 17 Feb 2023 11:42:34 +0200
From:   Mohammed Gamal <mgamal@...hat.com>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "xxiong@...hat.com" <xxiong@...hat.com>
Subject: Re: [PATCH v2] Drivers: vmbus: Check for channel allocation before
 looking up relids

On Fri, Feb 17, 2023 at 8:25 AM Dexuan Cui <decui@...rosoft.com> wrote:
>
> > From: Mohammed Gamal <mgamal@...hat.com>
> > Sent: Tuesday, February 14, 2023 3:28 AM
> > ...
> > So Make relid2channel() check if vmbus channels is allocated first, and if not
> > print a warning and return NULL to the caller.
> Can we change the above to:
>
> Print a warning and error out in relid2channel() for a channel id that's invalid
> in the second kernel.
Will do!

>
> > --- a/drivers/hv/connection.c
> > +++ b/drivers/hv/connection.c
> > @@ -409,6 +409,10 @@ void vmbus_disconnect(void)
> >   */
> >  struct vmbus_channel *relid2channel(u32 relid)
> >  {
> > +     if (vmbus_connection.channels == NULL) {
> > +             WARN(1, "Requested relid=%u, but channel mapping not
> > allocated!\n", relid);
>
> WARN() may be too noisy. I suggest we use pr_warn() instead.
>
Makes sense. Will use pr_warn() instead.

> Can we make the line a little shorter:
>         pr_warn("relid2channel: invalid channel id %u\n", relid);
>
I think this message could be a bit misleading. The problem here is
not that the relid
is invalid, but that the relid-to-channel mapping hasn't been
allocated by the second
kernel yet. An invalid relid could simply be the case where relid >=
MAX_CHANNEL_RELIDS.

May be something like:
     pr_warn("relid2channel: No channels mapped for relid %d\n, relid");
would be clearer?