Re: [PATCH bpf-next v2 02/16] xsk: Add getsockopt XDP_OPTIONS

[Maxim Mikityanskiy <maximmi@mellanox.com>]

On 2019-05-04 20:25, Björn Töpel wrote:
> On Tue, 30 Apr 2019 at 20:12, Maxim Mikityanskiy <maximmi@mellanox.com> wrote:
>>
>> Make it possible for the application to determine whether the AF_XDP
>> socket is running in zero-copy mode. To achieve this, add a new
>> getsockopt option XDP_OPTIONS that returns flags. The only flag
>> supported for now is the zero-copy mode indicator.
>>
>> Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
>> Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
>> Acked-by: Saeed Mahameed <saeedm@mellanox.com>
>> ---
>>   include/uapi/linux/if_xdp.h       |  7 +++++++
>>   net/xdp/xsk.c                     | 22 ++++++++++++++++++++++
>>   tools/include/uapi/linux/if_xdp.h |  7 +++++++
>>   3 files changed, 36 insertions(+)
>>
>> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
>> index caed8b1614ff..9ae4b4e08b68 100644
>> --- a/include/uapi/linux/if_xdp.h
>> +++ b/include/uapi/linux/if_xdp.h
>> @@ -46,6 +46,7 @@ struct xdp_mmap_offsets {
>>   #define XDP_UMEM_FILL_RING             5
>>   #define XDP_UMEM_COMPLETION_RING       6
>>   #define XDP_STATISTICS                 7
>> +#define XDP_OPTIONS                    8
>>
>>   struct xdp_umem_reg {
>>          __u64 addr; /* Start of packet data area */
>> @@ -60,6 +61,12 @@ struct xdp_statistics {
>>          __u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
>>   };
>>
>> +struct xdp_options {
>> +       __u32 flags;
>> +};
>> +
>> +#define XDP_OPTIONS_FLAG_ZEROCOPY (1 << 0)
> 
> Nit: The other flags doesn't use "FLAG" in its name, but that doesn't
> really matter.
> 
>> +
>>   /* Pgoff for mmaping the rings */
>>   #define XDP_PGOFF_RX_RING                        0
>>   #define XDP_PGOFF_TX_RING               0x80000000
>> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
>> index b68a380f50b3..998199109d5c 100644
>> --- a/net/xdp/xsk.c
>> +++ b/net/xdp/xsk.c
>> @@ -650,6 +650,28 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>>
>>                  return 0;
>>          }
>> +       case XDP_OPTIONS:
>> +       {
>> +               struct xdp_options opts;
>> +
>> +               if (len < sizeof(opts))
>> +                       return -EINVAL;
>> +
>> +               opts.flags = 0;
> 
> Maybe get rid of this, in favor of "opts = {}" if the structure grows?

I'm OK with any of these options. Should I respin the series, or can I 
follow up with the change in RCs if the series gets to 5.2?

Alexei, is it even possible to still make changes to this series? The 
window appears closed.

> 
>> +
>> +               mutex_lock(&xs->mutex);
>> +               if (xs->zc)
>> +                       opts.flags |= XDP_OPTIONS_FLAG_ZEROCOPY;
>> +               mutex_unlock(&xs->mutex);
>> +
>> +               len = sizeof(opts);
>> +               if (copy_to_user(optval, &opts, len))
>> +                       return -EFAULT;
>> +               if (put_user(len, optlen))
>> +                       return -EFAULT;
>> +
>> +               return 0;
>> +       }
>>          default:
>>                  break;
>>          }
>> diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
>> index caed8b1614ff..9ae4b4e08b68 100644
>> --- a/tools/include/uapi/linux/if_xdp.h
>> +++ b/tools/include/uapi/linux/if_xdp.h
>> @@ -46,6 +46,7 @@ struct xdp_mmap_offsets {
>>   #define XDP_UMEM_FILL_RING             5
>>   #define XDP_UMEM_COMPLETION_RING       6
>>   #define XDP_STATISTICS                 7
>> +#define XDP_OPTIONS                    8
>>
>>   struct xdp_umem_reg {
>>          __u64 addr; /* Start of packet data area */
>> @@ -60,6 +61,12 @@ struct xdp_statistics {
>>          __u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
>>   };
>>
>> +struct xdp_options {
>> +       __u32 flags;
>> +};
>> +
>> +#define XDP_OPTIONS_FLAG_ZEROCOPY (1 << 0)
>> +
>>   /* Pgoff for mmaping the rings */
>>   #define XDP_PGOFF_RX_RING                        0
>>   #define XDP_PGOFF_TX_RING               0x80000000
>> --
>> 2.19.1
>>