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  • Anton Anton anjo
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  1. Nov 21, 2023
    • David Woodhouse's avatar
      net: do not delete nics in net_cleanup() · 84f85eb9
      David Woodhouse authored 
      
In net_cleanup() we only need to delete the netdevs, as those may have
state which outlives Qemu when it exits, and thus may actually need to
be cleaned up on exit.

The nics, on the other hand, are owned by the device which created them.
Most devices don't bother to clean up on exit because they don't have
any state which will outlive Qemu... but XenBus devices do need to clean
up their nodes in XenStore, and do have an exit handler to delete them.

When the XenBus exit handler destroys the xen-net-device, it attempts
to delete its nic after net_cleanup() had already done so. And crashes.

Fix this by only deleting netdevs as we walk the list. As the comment
notes, we can't use QTAILQ_FOREACH_SAFE() as each deletion may remove
*multiple* entries, including the "safely" saved 'next' pointer. But
we can store the *previous* entry, since nics are safe.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: default avatarPaul Durrant <paul@xen.org>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      84f85eb9
    • Akihiko Odaki's avatar
      net: Update MemReentrancyGuard for NIC · 9050f976
      Akihiko Odaki authored 
      
Recently MemReentrancyGuard was added to DeviceState to record that the
device is engaging in I/O. The network device backend needs to update it
when delivering a packet to a device.

This implementation follows what bottom half does, but it does not add
a tracepoint for the case that the network device backend started
delivering a packet to a device which is already engaging in I/O. This
is because such reentrancy frequently happens for
qemu_flush_queued_packets() and is insignificant.

Fixes: CVE-2023-3019
Reported-by: default avatarAlexander Bulekov <alxndr@bu.edu>
Signed-off-by: default avatarAkihiko Odaki <akihiko.odaki@daynix.com>
Acked-by: default avatarAlexander Bulekov <alxndr@bu.edu>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      9050f976
    • Akihiko Odaki's avatar
      net: Provide MemReentrancyGuard * to qemu_new_nic() · 7d0fefdf
      Akihiko Odaki authored 
      
Recently MemReentrancyGuard was added to DeviceState to record that the
device is engaging in I/O. The network device backend needs to update it
when delivering a packet to a device.

In preparation for such a change, add MemReentrancyGuard * as a
parameter of qemu_new_nic().

Signed-off-by: default avatarAkihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: default avatarAlexander Bulekov <alxndr@bu.edu>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      7d0fefdf
  3. Nov 17, 2023
    • Markus Armbruster's avatar
      net: Fix a misleading error message · 0a4a1512
      Markus Armbruster authored 
      
The error message

    $ qemu-system-x86_64 -netdev user,id=net0,ipv6-net=fec0::0/
    qemu-system-x86_64: -netdev user,id=net0,ipv6-net=fec0::0/: Parameter 'ipv6-prefixlen' expects a number

points to ipv6-prefixlen instead of ipv6-net.  Fix:

    qemu-system-x86_64: -netdev user,id=net0,ipv6-net=fec0::0/: parameter 'ipv6-net' expects a number after '/'

Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-ID: <20231031111059.3407803-6-armbru@redhat.com>
      0a4a1512
  5. Nov 07, 2023
  7. Nov 01, 2023
    • Juan Quintela's avatar
      migration: Use VMSTATE_INSTANCE_ID_ANY for slirp · b23db4cd
      Juan Quintela authored 
      
Each user network conection create a new slirp instance.  We register
more than one slirp instance for number 0.

qemu-system-x86_64: -netdev user,id=hs1: savevm_state_handler_insert: Detected duplicate SaveStateEntry: id=slirp, instance_id=0x0
Broken pipe
../../../../../mnt/code/qemu/full/tests/qtest/libqtest.c:195: kill_qemu() tried to terminate QEMU process but encountered exit status 1 (expected 0)
Aborted (core dumped)

Reviewed-by: default avatarStefan Berger <stefanb@linux.ibm.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
Message-ID: <20231020090731.28701-6-quintela@redhat.com>
      b23db4cd
  9. Oct 20, 2023
  11. Oct 18, 2023
  13. Oct 06, 2023
  15. Oct 04, 2023
  17. Sep 29, 2023
  19. Sep 18, 2023
    • Peter Maydell's avatar
      net/tap: Avoid variable-length array · 6d7a53e9
      Peter Maydell authored 
      
Use a heap allocation instead of a variable length array in
tap_receive_iov().

The codebase has very few VLAs, and if we can get rid of them all we
can make the compiler error on new additions.  This is a defensive
measure against security bugs where an on-stack dynamic allocation
isn't correctly size-checked (e.g.  CVE-2021-3527).

Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarFrancisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      6d7a53e9
    • Peter Maydell's avatar
      net/dump: Avoid variable length array · c4cf6819
      Peter Maydell authored 
      
Use a g_autofree heap allocation instead of a variable length
array in dump_receive_iov().

The codebase has very few VLAs, and if we can get rid of them all we
can make the compiler error on new additions.  This is a defensive
measure against security bugs where an on-stack dynamic allocation
isn't correctly size-checked (e.g.  CVE-2021-3527).

Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarFrancisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      c4cf6819
    • Ilya Maximets's avatar
      net: add initial support for AF_XDP network backend · cb039ef3
      Ilya Maximets authored 
      
AF_XDP is a network socket family that allows communication directly
with the network device driver in the kernel, bypassing most or all
of the kernel networking stack.  In the essence, the technology is
pretty similar to netmap.  But, unlike netmap, AF_XDP is Linux-native
and works with any network interfaces without driver modifications.
Unlike vhost-based backends (kernel, user, vdpa), AF_XDP doesn't
require access to character devices or unix sockets.  Only access to
the network interface itself is necessary.

This patch implements a network backend that communicates with the
kernel by creating an AF_XDP socket.  A chunk of userspace memory
is shared between QEMU and the host kernel.  4 ring buffers (Tx, Rx,
Fill and Completion) are placed in that memory along with a pool of
memory buffers for the packet data.  Data transmission is done by
allocating one of the buffers, copying packet data into it and
placing the pointer into Tx ring.  After transmission, device will
return the buffer via Completion ring.  On Rx, device will take
a buffer form a pre-populated Fill ring, write the packet data into
it and place the buffer into Rx ring.

AF_XDP network backend takes on the communication with the host
kernel and the network interface and forwards packets to/from the
peer device in QEMU.

Usage example:

  -device virtio-net-pci,netdev=guest1,mac=00:16:35:AF:AA:5C
  -netdev af-xdp,ifname=ens6f1np1,id=guest1,mode=native,queues=1

XDP program bridges the socket with a network interface.  It can be
attached to the interface in 2 different modes:

1. skb - this mode should work for any interface and doesn't require
         driver support.  With a caveat of lower performance.

2. native - this does require support from the driver and allows to
            bypass skb allocation in the kernel and potentially use
            zero-copy while getting packets in/out userspace.

By default, QEMU will try to use native mode and fall back to skb.
Mode can be forced via 'mode' option.  To force 'copy' even in native
mode, use 'force-copy=on' option.  This might be useful if there is
some issue with the driver.

Option 'queues=N' allows to specify how many device queues should
be open.  Note that all the queues that are not open are still
functional and can receive traffic, but it will not be delivered to
QEMU.  So, the number of device queues should generally match the
QEMU configuration, unless the device is shared with something
else and the traffic re-direction to appropriate queues is correctly
configured on a device level (e.g. with ethtool -N).
'start-queue=M' option can be used to specify from which queue id
QEMU should start configuring 'N' queues.  It might also be necessary
to use this option with certain NICs, e.g. MLX5 NICs.  See the docs
for examples.

In a general case QEMU will need CAP_NET_ADMIN and CAP_SYS_ADMIN
or CAP_BPF capabilities in order to load default XSK/XDP programs to
the network interface and configure BPF maps.  It is possible, however,
to run with no capabilities.  For that to work, an external process
with enough capabilities will need to pre-load default XSK program,
create AF_XDP sockets and pass their file descriptors to QEMU process
on startup via 'sock-fds' option.  Network backend will need to be
configured with 'inhibit=on' to avoid loading of the program.
QEMU will need 32 MB of locked memory (RLIMIT_MEMLOCK) per queue
or CAP_IPC_LOCK.

There are few performance challenges with the current network backends.

First is that they do not support IO threads.  This means that data
path is handled by the main thread in QEMU and may slow down other
work or may be slowed down by some other work.  This also means that
taking advantage of multi-queue is generally not possible today.

Another thing is that data path is going through the device emulation
code, which is not really optimized for performance.  The fastest
"frontend" device is virtio-net.  But it's not optimized for heavy
traffic either, because it expects such use-cases to be handled via
some implementation of vhost (user, kernel, vdpa).  In practice, we
have virtio notifications and rcu lock/unlock on a per-packet basis
and not very efficient accesses to the guest memory.  Communication
channels between backend and frontend devices do not allow passing
more than one packet at a time as well.

Some of these challenges can be avoided in the future by adding better
batching into device emulation or by implementing vhost-af-xdp variant.

There are also a few kernel limitations.  AF_XDP sockets do not
support any kinds of checksum or segmentation offloading.  Buffers
are limited to a page size (4K), i.e. MTU is limited.  Multi-buffer
support implementation for AF_XDP is in progress, but not ready yet.
Also, transmission in all non-zero-copy modes is synchronous, i.e.
done in a syscall.  That doesn't allow high packet rates on virtual
interfaces.

However, keeping in mind all of these challenges, current implementation
of the AF_XDP backend shows a decent performance while running on top
of a physical NIC with zero-copy support.

Test setup:

2 VMs running on 2 physical hosts connected via ConnectX6-Dx card.
Network backend is configured to open the NIC directly in native mode.
The driver supports zero-copy.  NIC is configured to use 1 queue.

Inside a VM - iperf3 for basic TCP performance testing and dpdk-testpmd
for PPS testing.

iperf3 result:
 TCP stream      : 19.1 Gbps

dpdk-testpmd (single queue, single CPU core, 64 B packets) results:
 Tx only         : 3.4 Mpps
 Rx only         : 2.0 Mpps
 L2 FWD Loopback : 1.5 Mpps

In skb mode the same setup shows much lower performance, similar to
the setup where pair of physical NICs is replaced with veth pair:

iperf3 result:
  TCP stream      : 9 Gbps

dpdk-testpmd (single queue, single CPU core, 64 B packets) results:
  Tx only         : 1.2 Mpps
  Rx only         : 1.0 Mpps
  L2 FWD Loopback : 0.7 Mpps

Results in skb mode or over the veth are close to results of a tap
backend with vhost=on and disabled segmentation offloading bridged
with a NIC.

Signed-off-by: default avatarIlya Maximets <i.maximets@ovn.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> (docker/lcitool)
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      cb039ef3
    • Andrew Melnychenko's avatar
      virtio-net: Add USO flags to vhost support. · 9da16849
      Andrew Melnychenko authored 
      
New features are subject to check with vhost-user and vdpa.

Signed-off-by: default avatarYuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: default avatarAndrew Melnychenko <andrew@daynix.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      9da16849
    • Yuri Benditovich's avatar
      tap: Add check for USO features · f03e0cf6
      Yuri Benditovich authored 
      
Tap indicates support for USO features according to
capabilities of current kernel module.

Signed-off-by: default avatarYuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: default avatarAndrew Melnychecnko <andrew@daynix.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      f03e0cf6
    • Andrew Melnychenko's avatar
      tap: Add USO support to tap device. · 2ab0ec31
      Andrew Melnychenko authored 
      
Passing additional parameters (USOv4 and USOv6 offloads) when
setting TAP offloads

Signed-off-by: default avatarYuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: default avatarAndrew Melnychenko <andrew@daynix.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
      2ab0ec31
  21. Sep 13, 2023
  23. Sep 08, 2023
  25. Sep 07, 2023