linux-kernel - Re: [PATCH] xen/privcmd: make option visible in Kconfig

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Message-ID: <28809eae-ea8f-4f6b-b41a-a0895aec6e8c@t-8ch.de>
Date:   Mon, 15 Nov 2021 11:25:24 +0100
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Jan Beulich <jbeulich@...e.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen/privcmd: make option visible in Kconfig

On 2021-11-15 11:02+0100, Jan Beulich wrote:
> On 13.11.2021 09:38, Thomas Weißschuh wrote:
> > This configuration option provides a misc device as an API to userspace.
> > Make this API usable without having to select the module as a transitive
> > dependency.
> > 
> > This also fixes an issue where localyesconfig would select
> > CONFIG_XEN_PRIVCMD=m because it was not visible and defaulted to
> > building as module.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > 
> > ---
> > 
> > Note: If CONFIG_XEN_PRIVCMD really is only meant to be selected by
> > XENFS, then the issue can be fixed by removing its "default m"
> > definition.
> > ---
> >  drivers/xen/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> > index a1b11c62da9e..c14d8631b8f6 100644
> > --- a/drivers/xen/Kconfig
> > +++ b/drivers/xen/Kconfig
> > @@ -259,7 +259,7 @@ config XEN_SCSI_BACKEND
> >  	  if guests need generic access to SCSI devices.
> >  
> >  config XEN_PRIVCMD
> > -	tristate
> > +	tristate "Xen privileged domain-0 commands"
> >  	depends on XEN
> >  	default m
> 
> While I agree with adding a prompt here, I'm not sure why you've added
> "domain-0" to its wording. Aiui this interface is equally available in
> DomU-s, just that they would be able to only (successfully) use a more
> restricted set of hypercalls. Otherwise the XEN dependency would need
> to be changed to XEN_DOM0 at the same time as adding a prompt, or the
> prompt's visibility be restricted to XEN_DOM0.

I got it from comment at the top of privcmd.c.

To be honest I have no knowledge about Xen and only submitted this patch to get
rid of the spurious module in my localyesconfig.

I can try to find a better wording and submit a v2 but would also be happy if
somebody more knowledgeable about this module wrote a patch, which would
probably be easiest for everybody.

Thanks,
Thomas