Re: [Xen-devel] [PATCH v2] x86/mm: Add mem access rights to NPT

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

On Lu, 2018-06-18 at 09:39 -0600, Tamas K Lengyel wrote:
> On Mon, Jun 18, 2018 at 9:19 AM Alexandru Isaila
> <aisaila@xxxxxxxxxxxxxxx> wrote:
> >
> >
> > +static p2m_access_t p2m_get_access(struct p2m_domain *p2m,
> > unsigned long gfn)
> > +{
> > +    void *ptr;
> > +
> > +    ptr = radix_tree_lookup(&p2m->mem_access_settings, gfn);
> > +    if ( !ptr )
> > +        return p2m_access_rwx;
> > +    else
> > +        return radix_tree_ptr_to_int(ptr);
> > +}
> > +
> > +static void p2m_set_access(struct p2m_domain *p2m, unsigned long
> > gfn,
> > +                                      p2m_access_t a)
> > +{
> > +    int rc;
> > +
> Shouldn't there be some locking around the radix tree operations
> here?
> If not, why not?
The lock is in the p2m_set_mem_access() so that one entry is set at a
time. The radix tree operations are similar to the ones on ARM but if
we missed something I will appreciate the help in correcting the issue.

Thanks,
Alex
>
> >
> > +    if ( p2m_access_rwx == a )
> > +        radix_tree_delete(&p2m->mem_access_settings, gfn);
> > +
> > +    rc = radix_tree_insert(&p2m->mem_access_settings, gfn,
> > +                           radix_tree_int_to_ptr(a));
> > +    if ( rc == -EEXIST )
> > +        /* If a setting already exists, change it to the new one
> > */
> > +        radix_tree_replace_slot(
> > +            radix_tree_lookup_slot(
> > +                &p2m->mem_access_settings, gfn),
> > +            radix_tree_int_to_ptr(a));
> > +}
> > +

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