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Filename Latest commit message Latest commit date
Jia He 336c7260a7 vhost: vsock: kick send_pkt worker once device is started
commit 0b841030625cde5f784dd62aec72d6a766faae70 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 10:31:21 +02:00
arch arm64: vdso: Add -fasynchronous-unwind-tables to cflags 2020-05-06 08:15:17 +02:00
block blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget 2020-05-02 08:48:59 +02:00
certs
crypto crypto: rng - Fix a refcounting bug in crypto_rng_reset() 2020-04-17 10:50:16 +02:00
Documentation USB: hub: Revert commit bd0e6c9614 ("usb: hub: try old enumeration scheme first for high speed devices") 2020-04-29 16:33:14 +02:00
drivers vhost: vsock: kick send_pkt worker once device is started 2020-05-10 10:31:21 +02:00
fs nfs: Fix potential posix_acl refcnt leak in nfs3_set_acl 2020-05-06 08:15:16 +02:00
include NFSv4.1: fix handling of backchannel binding in BIND_CONN_TO_SESSION 2020-05-06 08:15:05 +02:00
init printk: queue wake_up_klogd irq_work only if per-CPU areas are ready 2020-05-02 08:48:42 +02:00
ipc ipc/util.c: sysvipc_find_ipc() should increase position index 2020-04-29 16:33:00 +02:00
kernel PM: hibernate: Freeze kernel threads in software_resume() 2020-05-06 08:15:09 +02:00
lib lib/raid6/test: fix build on distros whose /bin/sh is not bash 2020-04-29 16:33:00 +02:00
LICENSES
mm mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path 2020-05-02 08:48:54 +02:00
net net: use indirect call wrappers for skb_copy_datagram_iter() 2020-05-02 08:49:00 +02:00
samples vmalloc: fix remap_vmalloc_range() bounds checks 2020-04-29 16:33:14 +02:00
scripts kbuild: fix DT binding schema rule again to avoid needless rebuilds 2020-05-02 08:48:42 +02:00
security selinux: properly handle multiple messages in selinux_netlink_send() 2020-05-06 08:15:17 +02:00
sound ALSA: opti9xx: shut up gcc-10 range warning 2020-05-06 08:15:15 +02:00
tools objtool: Support Clang non-section symbols in ORC dump 2020-05-02 08:48:57 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
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.get_maintainer.ignore
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Kconfig
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Makefile Linux 5.4.39 2020-05-06 08:15:17 +02:00
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.

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.