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

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/8/22 18:55, Andrew Cooper wrote:
> 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" ?

Thanks for your reminder, I will add something to check this point.

I think the caller can compare that number of entries as that input 
parameter with the return value. If equal, this should be in case of 
"xen filled in N entries". If not, this is in case of "xen said you need 
N entries for all the information".

Thanks
Tiejun

>
> ~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,
>
>