On 2019-05-04 20:25, Björn Töpel wrote:

On Tue, 30 Apr 2019 at 20:12, Maxim Mikityanskiy [off-list ref] wrote:

quoted

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 <redacted>
Reviewed-by: Tariq Toukan <redacted>
Acked-by: Saeed Mahameed <redacted>
---
  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.

quoted

+
  /* 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.

quoted

+
+               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