Re: [Xen-devel] [PATCH 02/18] arm/altp2m: Add first altp2m HVMOP stubs.

[Julien Grall <julien.grall@xxxxxxx>]

Hello Sergej,

On 04/07/16 12:45, Sergej Proskurin wrote:
> +static int do_altp2m_op(XEN_GUEST_HANDLE_PARAM(void) arg)
> +{
> +    struct xen_hvm_altp2m_op a;
> +    struct domain *d = NULL;
> +    int rc = 0;
> +
> +    if ( !hvm_altp2m_supported() )
> +        return -EOPNOTSUPP;
> +
> +    if ( copy_from_guest(&a, arg, 1) )
> +        return -EFAULT;
> +
> +    if ( a.pad1 || a.pad2 ||
> +         (a.version != HVMOP_ALTP2M_INTERFACE_VERSION) ||
> +         (a.cmd < HVMOP_altp2m_get_domain_state) ||
> +         (a.cmd > HVMOP_altp2m_change_gfn) )
> +        return -EINVAL;
> +
> +    d = (a.cmd != HVMOP_altp2m_vcpu_enable_notify) ?
> +        rcu_lock_domain_by_any_id(a.domain) : rcu_lock_current_domain();
> +
> +    if ( d == NULL )
> +        return -ESRCH;
> +
> +    if ( (a.cmd != HVMOP_altp2m_get_domain_state) &&
> +         (a.cmd != HVMOP_altp2m_set_domain_state) &&
> +         !d->arch.altp2m_active )
> +    {
> +        rc = -EOPNOTSUPP;
> +        goto out;
> +    }
> +
> +    if ( (rc = xsm_hvm_altp2mhvm_op(XSM_TARGET, d)) )
> +        goto out;
I think this is the best place to ask a couple of questions related to 
who can access altp2m. Based on this call, a guest is allowed to manage 
its own altp2m. Can you explain why we would want a guest to do that?
Also, I have noticed that a guest is allowed to disable ALTP2M on ARM 
because it set any param (x86 has some restriction on it). Similarly, 
the ALTP2M parameter can be set multiple time.
Regards,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel