On 07/04/2017 03:18 AM, Michael S. Tsirkin wrote:
On Wed, Jun 28, 2017 at 10:37:59AM +0800, Wei Wang wrote:
This patch enables the virtio-net tx queue size to be configurable
between 256 (the default queue size) and 1024 by the user when the
vhost-user backend is used.
Currently, the maximum tx queue size for other backends is 512 due
to the following limitations:
- QEMU backend: the QEMU backend implementation in some cases may
send 1024+1 iovs to writev.
- Vhost_net backend: there are possibilities that the guest sends
a vring_desc of memory which crosses a MemoryRegion thereby
generating more than 1024 iovs after translation from guest-physical
address in the backend.
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
I was going to apply this, but run into a host of issues:
This segfaults:
$ ./x86_64-softmmu/qemu-system-x86_64 -device virtio-net,tx_queue_size=1024
Segmentation fault (core dumped)
I tried to tweak this code a bit to avoid the crash, and I run into a further
issue:
$ ./x86_64-softmmu/qemu-system-x86_64 -device virtio-net,tx_queue_size=1024
Bad ram offset aa49002
Aborted (core dumped)
the second issue is especially concerning.
AFAIK, all the virtio-net backends require "-netdev". I'm wondering if there
is any case that virtio-net can work without a "-netdev" created in QEMU?
If not, would it be better if we just stop the device creation at the
beginning of
virtio_net_device_realize() if "-netdev" is not given (i.e.
!n->nic_conf.peers.ncs[0])?
Best,
Wei
