Re: [Xen-devel] [PATCH v8 1/8] xen: xsm: flask: introduce XENMAPSPACE_gmfn_share for memory sharing

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 9 Oct 2018, Jan Beulich wrote:
> >>> On 09.10.18 at 01:37, <sstabellini@xxxxxxxxxx> wrote:
> > --- a/xen/include/xsm/dummy.h
> > +++ b/xen/include/xsm/dummy.h
> > @@ -535,6 +535,20 @@ static XSM_INLINE int 
> > xsm_map_gmfn_foreign(XSM_DEFAULT_ARG struct domain *d, str
> >      return xsm_default_action(action, d, t);
> >  }
> >  
> > +/*
> > + * Be aware that this is not an exact default equivalence of its flask
> > + * variant which also checks if @d and @t "are allowed to share memory
> > + * pages", for now, we don't have a proper default equivalence of such a
> > + * check.
> > + */
> > +static XSM_INLINE int xsm_map_gmfn_share(XSM_DEFAULT_ARG struct domain *d,
> > +                                         struct domain *t)
> > +{
> > +    XSM_ASSERT_ACTION(XSM_TARGET);
> > +    return xsm_default_action(XSM_TARGET, current->domain, d) ?:
> > +           xsm_default_action(action, current->domain, t);
> > +}
> 
> Does this (specifically xsm/dummy.c)) build with XSM enabled?
> Afaict "action" is going to be an undefined symbol in that case.

I tried it and it does build OK


> > --- a/xen/xsm/flask/hooks.c
> > +++ b/xen/xsm/flask/hooks.c
> > @@ -1192,6 +1192,14 @@ static int flask_map_gmfn_foreign(struct domain *d, 
> > struct domain *t)
> >      return domain_has_perm(d, t, SECCLASS_MMU, MMU__MAP_READ | 
> > MMU__MAP_WRITE);
> >  }
> >  
> > +static int flask_map_gmfn_share(struct domain *d, struct domain *t)
> > +{
> > +    if ( current_has_perm(d, SECCLASS_MMU, MMU__MAP_READ | MMU__MAP_WRITE) 
> > )
> > +        return rc;
> > +    return current_has_perm(t, SECCLASS_MMU, MMU__MAP_READ | 
> > MMU__MAP_WRITE) ?:
> > +           domain_has_perm(d, t, SECCLASS_MMU, MMU__SHARE_MEM);
> > +}
> > +
> 
> Same here, for "rc". It looks to me as if the first two lines of the function
> body were wrongly left in place anyway. But please could you at least
> build-test with XSM enabled when you make changes to XSM code?

This is a mistake. You are right the two lines need to be removed. I
build-tested it with XSM correctly.

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