Re: [PATCH for 4.6 v2 2/3] libxc: introduce xc_domain_getvnuma

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-09-09 at 18:03 +0100, Wei Liu wrote:
> A simple wrapper for XENMEM_get_vnumainfo.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

Some comments which are not specific to this patch:
 
> +int xc_domain_getvnuma(xc_interface *xch,
> +                       uint32_t domid,
> +                       uint32_t *nr_vnodes,
> +                       uint32_t *nr_vmemranges,
> +                       uint32_t *nr_vcpus,
> +                       xen_vmemrange_t *vmemrange,
> +                       unsigned int *vdistance,
> +                       unsigned int *vcpu_to_vnode)
> +{
> +    int rc;
> +    DECLARE_HYPERCALL_BOUNCE(vmemrange, sizeof(*vmemrange) * *nr_vmemranges,
> +                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> +    DECLARE_HYPERCALL_BOUNCE(vdistance, sizeof(*vdistance) *
> +                             *nr_vnodes * *nr_vnodes,
> +                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> +    DECLARE_HYPERCALL_BOUNCE(vcpu_to_vnode, sizeof(*vcpu_to_vnode) * *nr_vcpus,
> +                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> +
> +    struct xen_vnuma_topology_info vnuma_topo;
> +
> +    if ( xc_hypercall_bounce_pre(xch, vmemrange)      ||
> +         xc_hypercall_bounce_pre(xch, vdistance)      ||
> +         xc_hypercall_bounce_pre(xch, vcpu_to_vnode) )
> +    {
> +        rc = -1;
> +        errno = ENOMEM;

xc_hypercall_bounce_pre really ought to set errno, but it (to my surprise)
doesn't appear to do so...

> +        goto vnumaget_fail;
> +    }
> +
> +    set_xen_guest_handle(vnuma_topo.vmemrange.h, vmemrange);
> +    set_xen_guest_handle(vnuma_topo.vdistance.h, vdistance);
> +    set_xen_guest_handle(vnuma_topo.vcpu_to_vnode.h, vcpu_to_vnode);
> +
> +    vnuma_topo.nr_vnodes = *nr_vnodes;
> +    vnuma_topo.nr_vcpus = *nr_vcpus;
> +    vnuma_topo.nr_vmemranges = *nr_vmemranges;
> +    vnuma_topo.domid = domid;
> +    vnuma_topo.pad = 0;
> +
> +    rc = do_memory_op(xch, XENMEM_get_vnumainfo, &vnuma_topo,
> +                      sizeof(vnuma_topo));
> +
> +    *nr_vnodes = vnuma_topo.nr_vnodes;
> +    *nr_vcpus = vnuma_topo.nr_vcpus;
> +    *nr_vmemranges = vnuma_topo.nr_vmemranges;

We're a bit inconsistent, it seems, about a) tolerating such parameters
being NULL and b) whether or not we update them when the hypercall failed.

Anyway, neither of those are anything to block this patch over, so ack as
above.

> +
> + vnumaget_fail:
> +    xc_hypercall_bounce_post(xch, vmemrange);
> +    xc_hypercall_bounce_post(xch, vdistance);
> +    xc_hypercall_bounce_post(xch, vcpu_to_vnode);
> +
> +    return rc;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C,