RE: [PATCH v3 28/28] xen/domctl: wrap common/domctl.c with CONFIG_MGMT_HYPERCALLS

["Penny, Zheng" <penny.zheng@xxxxxxx>]

[Public]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Thursday, October 30, 2025 9:40 PM
> To: Penny, Zheng <penny.zheng@xxxxxxx>
> Cc: Huang, Ray <Ray.Huang@xxxxxxx>; oleksii.kurochko@xxxxxxxxx; Andrew
> Cooper <andrew.cooper3@xxxxxxxxxx>; Anthony PERARD
> <anthony.perard@xxxxxxxxxx>; Orzel, Michal <Michal.Orzel@xxxxxxx>; Julien
> Grall <julien@xxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>; Stefano
> Stabellini <sstabellini@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v3 28/28] xen/domctl: wrap common/domctl.c with
> CONFIG_MGMT_HYPERCALLS
>
> On 13.10.2025 12:15, Penny Zheng wrote:
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -646,11 +646,13 @@ config SYSTEM_SUSPEND
> >       If unsure, say N.
> >
> >  config MGMT_HYPERCALLS
> > -   def_bool y
> > +   bool "Enable privileged hypercalls for system management"
> >     help
> >       This option shall only be disabled on some dom0less systems, or
> >       PV shim on x86, to reduce Xen footprint via managing unnessary
> > -     hypercalls, like sysctl, etc.
> > +     hypercalls, like sysctl, domctl, etc.
> > +     Be cautious to disable it, as users will face missing a few basic
> > +     hypercalls like listdomains, getdomaininfo, etc.
>
> This is still too little, imo. For one I'm not sure "users" is quite the 
> right term. I'd say
> it's more "admins". And then, as mentioned, there are a few domctl-s which are
> usable by DMs. Aiui device pass-through may also be impacted, which imo will
> want mentioning here as well. Or else, if there is an implication that DMs 
> aren't to
> be used when MGMT_HYPERCALLS=n, that is what would want calling out.
>

How about
"
        Be cautious to disable it, as admins will face missing a few basic
        hypercalls like listdomains, getdomaininfo, etc, hence leading to
        have an impact on xl-device-passthrough and restricted DM.
"

Another question on PV_SHIM_EXCLUSIVE:
After Stefano's " 6c80f0dd1bb  xen: fix randconfig build problems after 
introducing SYSCTL " reversion patch, and to avoid incurring randconfig 
failures till the last, maybe I shall combine all PV_SHIM_EXCLUSIVE-related 
changes into a new commit and put it in the last, after making MGMT_HYPERCALLS 
optional again?

> Jan