94 Commits

Author SHA1 Message Date
Tiwei Bie
2a2904fa9c vhost: fix potential use-after-free for memory region
Reclaim outstanding zmbufs first before freeing memory regions,
otherwise there could be use-after-free.

Fixes: b0a985d1f340 ("vhost: add dequeue zero copy")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-03-01 18:17:36 +01:00
Tiwei Bie
d767436ee5 vhost: fix potential use-after-free for zero copy mbuf
Don't free the zero copy mbufs before they have been consumed,
otherwise there could be use-after-free.

Fixes: b0a985d1f340 ("vhost: add dequeue zero copy")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-03-01 18:17:36 +01:00
Tiwei Bie
041d37b2ef vhost: restore mbuf first when freeing zmbuf
The mbufs should also be restored in free_zmbufs().

Fixes: b0a985d1f340 ("vhost: add dequeue zero copy")
Fixes: 3ebd930588b7 ("vhost: fix mbuf free")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-03-01 18:17:35 +01:00
Tiwei Bie
4800639000 vhost: fix access for indirect descriptors
Fix a possible out of bound access which may happen when handling
indirect descs in split ring.

Fixes: 1be4ebb1c464 ("vhost: support indirect descriptor in mergeable Rx")
Cc: stable@dpdk.org

Reported-by: Haiyue Wang <haiyue.wang@intel.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-01-24 10:08:31 +01:00
Tiwei Bie
450539b47e vhost: fix possible dead loop in vector filling
Fix a possible dead loop which may happen, e.g. when driver
created a loop in the desc list and lens in descs are zero.

Fixes: fd68b4739d2c ("vhost: use buffer vectors in dequeue path")
Fixes: 2f3225a7d69b ("vhost: add vector filling support for packed ring")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-01-14 17:44:29 +01:00
Tiwei Bie
06fc8545fd vhost: fix possible out of bound access in vector filling
Fixes: 7f74b95c444f ("vhost: pre update used ring for Tx and Rx")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2019-01-14 17:44:29 +01:00
Maxime Coquelin
b473ec1131 vhost: batch used descs chains write-back with packed ring
Instead of writing back descriptors chains in order, let's
write the first chain flags last in order to improve batching.

Also, move the write barrier in logging cache sync, so that it
is done only when logging is enabled. It means there is now
one more barrier for split ring when logging is enabled.

With Kernel's pktgen benchmark, ~3% performance gain is measured.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
2018-12-21 16:22:41 +01:00
Maxime Coquelin
815814c4ff vhost: remove useless prefetch for packed ring descriptor
This prefetch does not show any performance improvement.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-12-21 16:22:41 +01:00
Maxime Coquelin
aaf8979d6f vhost: prefetch descriptor after the read barrier
This patch moves the prefetch after the available index
is read to avoid prefetching a descriptor not available yet.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-12-21 16:22:41 +01:00
Maxime Coquelin
33e12d63d1 vhost: enforce desc flags and content read ordering
A read barrier is required to ensure that the ordering between
descriptor's flags and content reads is enforced.

1. read flags = desc->flags
if (flags & AVAIL_BIT)
2.   read desc->id

There is a control dependency between steps 1 and step 2.
2 could be speculatively executed before 1, which could result
in 'id' to not be updated yet.

Fixes: 2f3225a7d69b ("vhost: add vector filling support for packed ring")
Cc: stable@dpdk.org

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-12-21 16:22:41 +01:00
Maxime Coquelin
d4ff2135eb vhost: enforce avail index and desc read ordering
A read barrier is required to ensure the ordering between
available index and the descriptor reads is enforced.

1. read avail_head = avail->idx
2. read cur_idx = last_avail_idx
if (cur_idx != avail_head) {
    3. read idx = avail->ring[cur_idx]
    4. read desc[idx]
}

There is a control dependency between step 1 and steps 3 & 4,
3 could be speculatively executed before 1, which could result
in 'idx' to not being updated yet.

Fixes: 4796ad63ba1f ("examples/vhost: import userspace vhost application")
Cc: stable@dpdk.org

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-12-21 16:22:41 +01:00
Xiao Wang
b13ad2decc vhost: provide helpers for virtio ring relay
This patch provides two helpers for vdpa device driver to perform a
relay between the guest virtio ring and a mediated virtio ring.

The available ring relay will synchronize the available entries, and
help to do desc validity checking.

The used ring relay will synchronize the used entries from mediated ring
to guest ring, and help to do dirty page logging for live migration.

The later patch will leverage these two helpers.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-12-21 16:22:40 +01:00
Tiwei Bie
30affaeebc vhost: fix IOVA access for packed ring
We should apply for RO access when receiving packets from the
VM and apply for RW access when sending packets to the VM.

Fixes: a922401f35cc ("vhost: add Rx support for packed ring")
Fixes: ae999ce49dcb ("vhost: add Tx support for packed ring")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-11-14 00:35:53 +01:00
Maxime Coquelin
e988a6d845 vhost: avoid memory barriers when no descriptors dequeued
In both split and packed dequeue paths, flush_shadow_used_ring
and vhost_ring_call variants gets called even if not packets
have been dequeued, and so no descriptors updates happened.

It has an impact on CPU pipeline, as memory barriers are used
in these functions.

This patch don't call these functions if no descriptors have
been dequeued. The performance gain with split ring when
dequeue zero-copy is disabled should be null, but should be
noticeable with packed ring or dequeue zero-copy enabled.

Fixes: ae999ce49dcb ("vhost: add Tx support for packed ring")
Fixes: 915cf9404225 ("vhost: use shadow used ring in dequeue path")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
Tested-by: Jens Freimann <jfreimann@redhat.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
2018-10-26 22:14:06 +02:00
Tiwei Bie
16b9e38e74 vhost: fix vector filling for packed ring
We should return the length of the buffers described by
the current descriptor chain after filling the buffer
vector. So we need to zero the *len first.

Fixes: 2f3225a7d69b ("vhost: add vector filling support for packed ring")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-10-26 22:14:05 +02:00
Jiayu Hu
729199397f vhost: fix corner case for enqueue operation
When performing enqueue operations on the split and packed rings,
if the reserved buffer length from the descriptor table exceeds
65535, the returned length by fill_vec_buf_split/_packed()
overflows. This patch is to avoid this corner case.

Fixes: f689586bc060 ("vhost: shadow used ring update")
Fixes: fd68b4739d2c ("vhost: use buffer vectors in dequeue path")
Fixes: 2f3225a7d69b ("vhost: add vector filling support for packed ring")
Fixes: 37f5e79a271d ("vhost: add shadow used ring support for packed rings")
Fixes: a922401f35cc ("vhost: add Rx support for packed ring")
Fixes: ae999ce49dcb ("vhost: add Tx support for packed ring")
Cc: stable@dpdk.org

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-09-28 01:41:03 +02:00
Tiwei Bie
58e90a9113 vhost: fix return value on enqueue path
Fixes: 62250c1d0978 ("vhost: extract split ring handling from Rx and Tx functions")
Fixes: a922401f35cc ("vhost: add Rx support for packed ring")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-09-14 20:08:41 +02:00
Tiwei Bie
adead74939 vhost: remove unused variable
The nr_updated is just increased and not really used.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
2018-08-02 04:41:49 +02:00
Tiwei Bie
0989161b26 vhost: release locks on RARP packet failure
Fixes: eefac9536a90 ("vhost: postpone device creation until rings are mapped")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
2018-07-26 10:02:52 +02:00
Tiwei Bie
14962a9c4f vhost: fix overflow on shadow used ring
The shadow used ring's size is the same as the vq's size,
so we shouldn't try more than "vq size" times. Besides,
the element pointed by avail->idx isn't available to the
device, so we will return error when try "vq size" times.

Fixes: 24e4844048e1 ("vhost: unify Rx mergeable and non-mergeable paths")
Fixes: a922401f35cc ("vhost: add Rx support for packed ring")

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
2018-07-26 10:02:50 +02:00
Jiayu Hu
6e2fad861a vhost: fix return value on dequeue path
This patch fixes the incorrect return value for rte_vhost_dequeue_burst()
when virtqueue is not enabled or virtqueue address translation fails.

Fixes: 62250c1d0978 ("vhost: extract split ring handling from Rx and Tx functions")

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-26 10:02:43 +02:00
Tiwei Bie
04651f72d1 vhost: fix buffer length calculation
Fixes: fd68b4739d2c ("vhost: use buffer vectors in dequeue path")

Reported-by: Yinan Wang <yinan.wang@intel.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Acked-by: Zhihong Wang <zhihong.wang@intel.com>
Tested-by: Yinan Wang <yinan.wang@intel.com>
2018-07-23 23:55:26 +02:00
Maxime Coquelin
b1cce26af1 vhost: add notification for packed ring
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
ae999ce49d vhost: add Tx support for packed ring
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
a922401f35 vhost: add Rx support for packed ring
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
2f3225a7d6 vhost: add vector filling support for packed ring
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
cf3af2be49 vhost: create descriptor mapping function
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
37f5e79a27 vhost: add shadow used ring support for packed rings
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
3e2f9700bb vhost: append shadow used ring function names with split
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
62250c1d09 vhost: extract split ring handling from Rx and Tx functions
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
2c22b14388 vhost: clear batch copy index at copy time
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
d6315ce796 vhost: make indirect desc table copy desc type agnostic
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
7e47bba30a vhost: clear shadow used table index at flush time
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:19:29 +02:00
Maxime Coquelin
611994fc1b vhost: improve prefetching in enqueue path
This is an optimization to prefetch next buffer while the
current one is being processed.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:13:36 +02:00
Maxime Coquelin
c1058a6b16 vhost: prefetch first descriptor in dequeue path
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:13:36 +02:00
Maxime Coquelin
380a2adff3 vhost: improve prefetching in dequeue path
This is an optimization to prefetch next buffer while the
current one is being processed.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:13:36 +02:00
Maxime Coquelin
fd68b4739d vhost: use buffer vectors in dequeue path
To ease packed ring layout integration, this patch makes
the dequeue path to re-use buffer vectors implemented for
enqueue path.

Doing this, copy_desc_to_mbuf() is now ring layout type
agnostic.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:13:36 +02:00
Maxime Coquelin
915cf94042 vhost: use shadow used ring in dequeue path
Relax used ring contention by reusing the shadow used
ring feature used by enqueue path.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
2018-07-10 23:13:36 +02:00
Maxime Coquelin
c89e52d9c8 vhost: improve batched copies performance
Instead of copying batch_copy_nb_elems into the stack,
this patch uses it directly.

Small performance gain of 3% is seen when running PVP
benchmark.

Acked-by: Zhihong Wang <zhihong.wang@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-06-14 19:27:50 +02:00
Maxime Coquelin
24e4844048 vhost: unify Rx mergeable and non-mergeable paths
This patch reworks the vhost enqueue path so that a single
code path is used for both Rx mergeable or non-mergeable cases.

Acked-by: Zhihong Wang <zhihong.wang@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-06-14 19:27:50 +02:00
Maxime Coquelin
c16915b871 vhost: improve dirty pages logging performance
This patch caches all dirty pages logging until the used ring index
is updated.

The goal of this optimization is to fix a performance regression
introduced when the vhost library started to use atomic operations
to set bits in the shared dirty log map. While the fix was valid
as previous implementation wasn't safe against concurrent accesses,
contention was induced.

With this patch, during migration, we have:
1. Less atomic operations as only a single atomic OR operation
per 32 or 64 (depending on CPU) pages.
2. Less atomic operations as during a burst, the same page will
be marked dirty only once.
3. Less write memory barriers.

Fixes: 897f13a1f726 ("vhost: make page logging atomic")
Cc: stable@dpdk.org

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
2018-05-17 14:19:05 +02:00
Maxime Coquelin
8eac207d49 vhost: fix header copy to discontiguous desc buffer
In the loop to copy virtio-net header to the descriptor buffer,
destination pointer was incremented instead of the source
pointer.

Fixes: fb3815cc614d ("vhost: handle virtually non-contiguous buffers in Rx-mrg")
Fixes: 6727f5a739b6 ("vhost: handle virtually non-contiguous buffers in Rx")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-05-14 22:31:03 +01:00
Maxime Coquelin
fb3815cc61 vhost: handle virtually non-contiguous buffers in Rx-mrg
This patch enables the handling of buffers non-contiguous in
process virtual address space in the enqueue path when mergeable
buffers are used.

When virtio-net header doesn't fit in a single chunck, it is
computed in a local variable and copied to the buffer chuncks
afterwards.

For packet content, the copy length is limited to the chunck
size, next chuncks VAs being fetched afterward.

This issue has been assigned CVE-2018-1059.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 17:12:13 +02:00
Maxime Coquelin
6727f5a739 vhost: handle virtually non-contiguous buffers in Rx
This patch enables the handling of buffers non-contiguous in
process virtual address space in the enqueue path when mergeable
buffers aren't used.

When virtio-net header doesn't fit in a single chunck, it is
computed in a local variable and copied to the buffer chuncks
afterwards.

For packet content, the copy length is limited to the chunck
size, next chuncks VAs being fetched afterward.

This issue has been assigned CVE-2018-1059.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 17:12:13 +02:00
Maxime Coquelin
91b7b40806 vhost: handle virtually non-contiguous buffers in Tx
This patch enables the handling of buffers non-contiguous in
process virtual address space in the dequeue path.

When virtio-net header doesn't fit in a single chunck, it is
copied into a local variablei before being processed.

For packet content, the copy length is limited to the chunck
size, next chuncks VAs being fetched afterward.

This issue has been assigned CVE-2018-1059.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 17:12:13 +02:00
Maxime Coquelin
d0c24508e1 vhost: add support for non-contiguous indirect descs tables
This patch adds support for non-contiguous indirect descriptor
tables in VA space.

When it happens, which is unlikely, a table is allocated and the
non-contiguous content is copied into it.

This issue has been assigned CVE-2018-1059.

Reported-by: Yongji Xie <xieyongji@baidu.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 16:04:30 +02:00
Maxime Coquelin
070aceda33 vhost: check all range is mapped when translating GPAs
There is currently no check done on the length when translating
guest addresses into host virtual addresses. Also, there is no
guanrantee that the guest addresses range is contiguous in
the host virtual address space.

This patch prepares vhost_iova_to_vva() and its callers to
return and check the mapped size. If the mapped size is smaller
than the requested size, the caller handle it as an error.

This issue has been assigned CVE-2018-1059.

Reported-by: Yongji Xie <xieyongji@baidu.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 16:04:30 +02:00
Maxime Coquelin
c6ae7de0de vhost: fix indirect descriptors table translation size
This patch fixes the size passed at the indirect descriptor
table translation time, which is the len field of the descriptor,
and not a single descriptor.

This issue has been assigned CVE-2018-1059.

Fixes: 62fdb8255ae7 ("vhost: use the guest IOVA to host VA helper")

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-04-23 16:04:30 +02:00
Tomasz Kulasek
06fc115977 vhost: fix log macro name conflict
LOG_DEBUG is a symbol defined by POSIX, so if sys/log.h is
included the symbols conflict.

This patch changes LOG_DEBUG to VHOST_LOG_DEBUG.

Fixes: 1c01d52392d5 ("vhost: add debug print")
Cc: stable@dpdk.org

Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Signed-off-by: Tomasz Kulasek <tomaszx.kulasek@intel.com>
Reviewed-by: Jianfeng Tan <jianfeng.tan@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2018-03-30 14:08:42 +02:00
Stefan Hajnoczi
1c717af4c6 vhost: add flag for built-in virtio driver
The librte_vhost API is used in two ways:
1. As a vhost net device backend via rte_vhost_enqueue/dequeue_burst().
2. As a library for implementing vhost device backends.

There is no distinction between the two at the API level or in the
librte_vhost implementation.  For example, device state is kept in
"struct virtio_net" regardless of whether this is actually a net device
backend or whether the built-in virtio_net.c driver is in use.

The virtio_net.c driver should be a librte_vhost API client just like
the vhost-scsi code and have no special access to vhost.h internals.
Unfortunately, fixing this requires significant librte_vhost API
changes.

This patch takes a different approach: keep the librte_vhost API
unchanged but track whether the built-in virtio_net.c driver is in use.
See the next patch for a bug fix that requires knowledge of whether
virtio_net.c is in use.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
2018-02-05 15:11:07 +01:00