linux/include
Björn Töpel bbff2f321a xsk: new descriptor addressing scheme
Currently, AF_XDP only supports a fixed frame-size memory scheme where
each frame is referenced via an index (idx). A user passes the frame
index to the kernel, and the kernel acts upon the data.  Some NICs,
however, do not have a fixed frame-size model, instead they have a
model where a memory window is passed to the hardware and multiple
frames are filled into that window (referred to as the "type-writer"
model).

By changing the descriptor format from the current frame index
addressing scheme, AF_XDP can in the future be extended to support
these kinds of NICs.

In the index-based model, an idx refers to a frame of size
frame_size. Addressing a frame in the UMEM is done by offseting the
UMEM starting address by a global offset, idx * frame_size + offset.
Communicating via the fill- and completion-rings are done by means of
idx.

In this commit, the idx is removed in favor of an address (addr),
which is a relative address ranging over the UMEM. To convert an
idx-based address to the new addr is simply: addr = idx * frame_size +
offset.

We also stop referring to the UMEM "frame" as a frame. Instead it is
simply called a chunk.

To transfer ownership of a chunk to the kernel, the addr of the chunk
is passed in the fill-ring. Note, that the kernel will mask addr to
make it chunk aligned, so there is no need for userspace to do
that. E.g., for a chunk size of 2k, passing an addr of 2048, 2050 or
3000 to the fill-ring will refer to the same chunk.

On the completion-ring, the addr will match that of the Tx descriptor,
passed to the kernel.

Changing the descriptor format to use chunks/addr will allow for
future changes to move to a type-writer based model, where multiple
frames can reside in one chunk. In this model passing one single chunk
into the fill-ring, would potentially result in multiple Rx
descriptors.

This commit changes the uapi of AF_XDP sockets, and updates the
documentation.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-06-04 17:21:02 +02:00
..
acpi xen: fixes for 4.17-rc1 2018-04-12 11:04:35 -07:00
asm-generic earlycon: Use a pointer table to fix __earlycon_table stride 2018-04-23 10:06:59 +02:00
clocksource
crypto
drm drm: Fix HDCP downstream dev count read 2018-04-16 12:10:48 -04:00
dt-bindings Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-05-11 20:53:22 -04:00
keys
kvm KVM: arm/arm64: vgic: Fix source vcpu issues for GICv2 SGI 2018-04-27 12:39:09 +01:00
linux bpf: implement bpf_get_current_cgroup_id() helper 2018-06-03 18:22:41 -07:00
math-emu
media MAINTAINERS & files: Canonize the e-mails I use at files 2018-05-04 06:21:06 -04:00
memory
misc
net xdp: done implementing ndo_xdp_xmit flush flag for all drivers 2018-06-03 08:11:34 -07:00
pcmcia
ras
rdma IB/uverbs: Fix uverbs_attr_get_obj 2018-05-23 15:25:53 -06:00
scsi scsi: core: remove reference to scsi_show_extd_sense() 2018-04-18 23:37:39 -04:00
soc soc: bcm2835: Make !RASPBERRYPI_FIRMWARE dummies return failure 2018-04-16 15:15:23 -07:00
sound ALSA: control: Hardening for potential Spectre v1 2018-04-25 10:37:46 +02:00
target
trace net/ipv4: Remove tracepoint in fib_validate_source 2018-05-24 23:01:15 -04:00
uapi xsk: new descriptor addressing scheme 2018-06-04 17:21:02 +02:00
video
xen xen/sndif: Sync up with the canonical definition in Xen 2018-04-17 08:26:33 -04:00