Re: [PATCH 1/8] tools/xenstored: allow domU to get own features

[Jürgen Groß <jgross@xxxxxxxx>]

On 20.04.26 23:28, Jason Andryuk wrote:
> On 2026-03-13 03:47, Juergen Gross wrote:
> > Expand the XS_GET_FEATURE command to allow an unprivileged domain to
> > read its own available features. While this information is available
> > via the related field in the shared page used for communication with
> > Xenstore, user land components of the domU would need special support
> > in the related kernel driver to obtain that data. With supporting the
> > XS_GET_FEATURE for that purpose, only an up to date libxenstore is
> > needed.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> >   docs/misc/xenstore.txt   |  9 +++++----
> >   tools/xenstored/core.c   |  3 +--
> >   tools/xenstored/domain.c | 16 +++++++++++-----
> >   3 files changed, 17 insertions(+), 11 deletions(-)
> >
> > diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
> > index 4eccbc2f7f..8a2c19d116 100644
> > --- a/docs/misc/xenstore.txt
> > +++ b/docs/misc/xenstore.txt
> > @@ -427,13 +427,14 @@ SET_FEATURE        <domid>|<value>|
> >       to set a bit for a feature not being supported by the running
> >       Xenstore will be denied. Providing no <domid> with the
> >       GET_FEATURE command will return the features which are supported
> > -    by Xenstore.
> > +    by Xenstore for the domain issuing the command.
> >       SET_FEATURE for a domain will be rejected after the INTRODUCE
> > -    command for this domain has been sent to xenstored.
> > +    command for this domain has been sent to xenstored. This has the
> > +    effect that dom0 will always have all supported features enabled.
> This statement...
>
> > --- a/tools/xenstored/domain.c
> > +++ b/tools/xenstored/domain.c
> > @@ -1293,17 +1293,23 @@ int do_get_feature(const void *ctx, struct connection 
> > *conn,
> >       char *result;
> >       n_args = get_strings(in, vec, ARRAY_SIZE(vec));
> > -    if (n_args > 1)
> > -        return EINVAL;
> > -    if (n_args == 1) {
> > +    if (!n_args) {
> > +        features = conn->domain ? conn->domain->features
> > +                    : XENSTORE_FEATURES;
> ... cover this, yes?  With a stubdom, dom0 will have conn->domain. conn->domain- 
>  >features is initialized to XENSTORE_FEATURES and cannot change.  Provided that 
> is correct:
This is correct.

> Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Thanks,


Juergen

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