Re: [v4][PATCH 3/9] tools:libxc: introduce hypercall for xc_reserved_device_memory_map

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 22/08/14 11:09, Tiejun Chen wrote:
> We will introduce that hypercall xc_reserved_device_memory_map
> to libxc.
>
> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
> ---
>  tools/libxc/xc_domain.c | 29 +++++++++++++++++++++++++++++
>  tools/libxc/xenctrl.h   |  4 ++++
>  2 files changed, 33 insertions(+)
>
> diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
> index c67ac9a..08dc16f 100644
> --- a/tools/libxc/xc_domain.c
> +++ b/tools/libxc/xc_domain.c
> @@ -649,6 +649,35 @@ int xc_domain_set_memory_map(xc_interface *xch,
>  
>      return rc;
>  }
> +
> +int xc_reserved_device_memory_map(xc_interface *xch,
> +                                  struct xen_reserved_device_memory entries[],
> +                                  uint32_t max_entries)
> +{
> +    int rc;
> +    struct xen_reserved_device_memory_map memmap = {
> +        .nr_entries = max_entries
> +    };
> +    DECLARE_HYPERCALL_BOUNCE(entries,
> +                             sizeof(struct xen_reserved_device_memory) *
> +                             max_entries, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> +
> +    if ( xc_hypercall_bounce_pre(xch, entries) )
> +        return -1;
> +
> +    set_xen_guest_handle(memmap.buffer, entries);
> +
> +    rc = do_memory_op(xch, XENMEM_reserved_device_memory_map,
> +                      &memmap, sizeof(memmap));
> +
> +    xc_hypercall_bounce_post(xch, entries);
> +
> +    if ( errno == ENOBUFS )
> +        return memmap.nr_entries;
> +
> +    return rc ? -errno : memmap.nr_entries;

So how does the caller distinguish between "xen filled in N entries" and
"xen said you need N entries for all the information" ?

~Andrew

> +}
> +
>  int xc_get_machine_memory_map(xc_interface *xch,
>                                struct e820entry entries[],
>                                uint32_t max_entries)
> diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
> index 1c5d0db..1cc7852 100644
> --- a/tools/libxc/xenctrl.h
> +++ b/tools/libxc/xenctrl.h
> @@ -1270,6 +1270,10 @@ int xc_domain_set_memory_map(xc_interface *xch,
>  int xc_get_machine_memory_map(xc_interface *xch,
>                                struct e820entry entries[],
>                                uint32_t max_entries);
> +
> +int xc_reserved_device_memory_map(xc_interface *xch,
> +                                  struct xen_reserved_device_memory entries[],
> +                                  uint32_t max_entries);
>  #endif
>  int xc_domain_set_time_offset(xc_interface *xch,
>                                uint32_t domid,