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Alexander Lobakin 613f9d1f15 xsk: Respect device's headroom and tailroom on generic xmit path 
[ Upstream commit 3914d88f76 ]

xsk_generic_xmit() allocates a new skb and then queues it for
xmitting. The size of new skb's headroom is desc->len, so it comes
to the driver/device with no reserved headroom and/or tailroom.
Lots of drivers need some headroom (and sometimes tailroom) to
prepend (and/or append) some headers or data, e.g. CPU tags,
device-specific headers/descriptors (LSO, TLS etc.), and if case
of no available space skb_cow_head() will reallocate the skb.
Reallocations are unwanted on fast-path, especially when it comes
to XDP, so generic XSK xmit should reserve the spaces declared in
dev->needed_headroom and dev->needed tailroom to avoid them.

Note on max(NET_SKB_PAD, L1_CACHE_ALIGN(dev->needed_headroom)):

Usually, output functions reserve LL_RESERVED_SPACE(dev), which
consists of dev->hard_header_len + dev->needed_headroom, aligned
by 16.

However, on XSK xmit hard header is already here in the chunk, so
hard_header_len is not needed. But it'd still be better to align
data up to cacheline, while reserving no less than driver requests
for headroom. NET_SKB_PAD here is to double-insure there will be
no reallocations even when the driver advertises no needed_headroom,
but in fact need it (not so rare case).

Fixes: 35fcde7f8d ("xsk: support for Tx")
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210218204908.5455-5-alobakin@pm.me
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-14 09:50:28 +02:00
arch perf/amd/uncore: Fix sysfs type mismatch 2021-05-14 09:50:28 +02:00
block block: return -EBUSY when there are open partitions in blkdev_reread_part 2021-04-28 13:39:59 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 11:37:59 +01:00
crypto async_xor: increase src_offs when dropping destination page 2021-05-14 09:49:59 +02:00
Documentation media: docs: Fix data organization of MEDIA_BUS_FMT_RGB101010_1X30 2021-05-14 09:50:23 +02:00
drivers drivers/block/null_blk/main: Fix a double free in null_init. 2021-05-14 09:50:28 +02:00
fs io_uring: fix overflows checks in provide buffers 2021-05-14 09:50:28 +02:00
include security: keys: trusted: fix TPM2 authorizations 2021-05-14 09:50:20 +02:00
init seccomp: Fix CONFIG tests for Seccomp_filters 2021-05-14 09:50:24 +02:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel sched/debug: Fix cgroup_path[] serialization 2021-05-14 09:50:28 +02:00
lib crypto: poly1305 - fix poly1305_core_setkey() declaration 2021-05-14 09:50:13 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm: ptdump: fix build failure 2021-04-21 13:00:57 +02:00
net xsk: Respect device's headroom and tailroom on generic xmit path 2021-05-14 09:50:28 +02:00
samples samples, bpf: Add missing munmap in xdpsock 2021-03-17 17:06:12 +01:00
scripts kasan: fix hwasan build for gcc 2021-04-28 13:40:02 +02:00
security security: keys: trusted: fix TPM2 authorizations 2021-05-14 09:50:20 +02:00
sound ALSA: hda/realtek: Fix speaker amp on HP Envy AiO 32 2021-05-14 09:50:03 +02:00
tools selftests: fix prepending $(OUTPUT) to $(TEST_PROGS) 2021-05-14 09:50:24 +02:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Stop looking for coalesced MMIO zones if the bus is destroyed 2021-05-14 09:50:04 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: move the staging subsystem to lists.linux.dev 2021-03-25 09:04:18 +01:00
Makefile Linux 5.10.36 2021-05-11 14:47:41 +02:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.