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Jia He a9ca8a3bda vhost: vsock: kick send_pkt worker once device is started 
commit 0b84103062 upstream.

Ning Bo reported an abnormal 2-second gap when booting Kata container [1].
The unconditional timeout was caused by VSOCK_DEFAULT_CONNECT_TIMEOUT of
connecting from the client side. The vhost vsock client tries to connect
an initializing virtio vsock server.

The abnormal flow looks like:
host-userspace           vhost vsock                       guest vsock
==============           ===========                       ============
connect()     -------->  vhost_transport_send_pkt_work()   initializing
   |                     vq->private_data==NULL
   |                     will not be queued
   V
schedule_timeout(2s)
                         vhost_vsock_start()  <---------   device ready
                         set vq->private_data

wait for 2s and failed
connect() again          vq->private_data!=NULL         recv connecting pkt

Details:
1. Host userspace sends a connect pkt, at that time, guest vsock is under
   initializing, hence the vhost_vsock_start has not been called. So
   vq->private_data==NULL, and the pkt is not been queued to send to guest
2. Then it sleeps for 2s
3. After guest vsock finishes initializing, vq->private_data is set
4. When host userspace wakes up after 2s, send connecting pkt again,
   everything is fine.

As suggested by Stefano Garzarella, this fixes it by additional kicking the
send_pkt worker in vhost_vsock_start once the virtio device is started. This
makes the pending pkt sent again.

After this patch, kata-runtime (with vsock enabled) boot time is reduced
from 3s to 1s on a ThunderX2 arm64 server.

[1] https://github.com/kata-containers/runtime/issues/1917

Reported-by: Ning Bo <n.b@live.com>
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jia He <justin.he@arm.com>
Link: https://lore.kernel.org/r/20200501043840.186557-1-justin.he@arm.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-05-10 10:30:05 +02:00
arch bpf, x86_32: Fix clobbering of dst for BPF_JSET 2020-05-02 17:26:00 +02:00
block block, bfq: fix use-after-free in bfq_idle_slice_timer_body 2020-04-17 10:48:42 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: api - Fix race condition in crypto_spawn_alg 2020-02-11 04:34:05 -08:00
Documentation arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419 2020-04-29 16:31:08 +02:00
drivers vhost: vsock: kick send_pkt worker once device is started 2020-05-10 10:30:05 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs btrfs: transaction: Avoid deadlock due to bad initialization timing of fs_info::journal_info 2020-05-06 08:13:33 +02:00
include qed: Fix use after free in qed_chain_free 2020-05-02 17:26:00 +02:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/util.c: sysvipc_find_ipc() should increase position index 2020-04-29 16:31:13 +02:00
kernel PM: hibernate: Freeze kernel threads in software_resume() 2020-05-06 08:13:28 +02:00
lib lib/raid6: use vdupq_n_u8 to avoid endianness warnings 2020-04-23 10:30:15 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path 2020-05-02 17:25:54 +02:00
net svcrdma: Fix leak of svc_rdma_recv_ctxt objects 2020-05-02 17:25:52 +02:00
samples vmalloc: fix remap_vmalloc_range() bounds checks 2020-04-29 16:31:27 +02:00
scripts kconfig: qconf: Fix a few alignment issues 2020-04-29 16:31:13 +02:00
security selinux: properly handle multiple messages in selinux_netlink_send() 2020-05-06 08:13:32 +02:00
sound ALSA: opti9xx: shut up gcc-10 range warning 2020-05-06 08:13:32 +02:00
tools objtool: Support Clang non-section symbols in ORC dump 2020-05-02 17:25:57 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt x86/kvm: Cache gfn to pfn translation 2020-04-29 16:31:19 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:38:49 +01:00
Makefile Linux 4.19.121 2020-05-06 08:13:35 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.