Re: [PATCH for-4.14] mm: fix public declaration of struct xen_mem_acquire_resource

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Jun 23, 2020 at 05:04:53PM +0200, Jan Beulich wrote:
> On 23.06.2020 15:52, Roger Pau Monne wrote:
> > XENMEM_acquire_resource and it's related structure is currently inside
> > a __XEN__ or __XEN_TOOLS__ guarded section to limit it's scope to the
> > hypervisor or the toolstack only. This is wrong as the hypercall is
> > already being used by the Linux kernel at least, and as such needs to
> > be public.
> 
> Actually - how does this work for the Linux kernel, seeing
> 
>     rc = rcu_lock_remote_domain_by_id(xmar.domid, &d);
>     if ( rc )
>         return rc;
> 
>     rc = xsm_domain_resource_map(XSM_DM_PRIV, d);
>     if ( rc )
>         goto out;
> 
> in the function?

It's my understanding (I haven't tried to use that hypercall yet on
FreeBSD, so I cannot say I've tested it), that xmar.domid is the
remote domain, which the functions locks and then uses
xsm_domain_resource_map to check whether the current domain has
permissions to do privileged operations against it.

Roger.