[RFC 0/2] Add risc-v vhost-net support

[Yifei Jiang]

Hi,

These two patches enable support for vhost-net on RISC-V architecture. They are developed
based on the Linux source in this repo: https://github.com/avpatel/linux,
the branch is riscv_kvm_v13. 

The accompanying QEMU is from the repo: https://github.com/alistair23/qemu, the branch is
hyp-ext-v0.6.next. In order for the QEMU to work with KVM, the patch found here is necessary:
https://patchwork.kernel.org/cover/11435965/

Several steps to use this:

1. create virbr0 on riscv64 emulation
$ brctl addbr virbr0
$ brctl stp virbr0 on
$ ifconfig virbr0 up
$ ifconfig virbr0 <virbr0_ip> netmask <virbr0_netmask>

2. boot riscv64 guestOS on riscv64 emulation
$ ./qemu-system-riscv64 -M virt,accel=kvm -m 1024M -cpu host -nographic \
	-name guest=riscv-guest \
	-smp 2 \
	-kernel ./Image \
	-drive file=./guest.img,format=raw,id=hd0 \
	-device virtio-blk,drive=hd0 \
	-netdev type=tap,vhost=on,script=./ifup.sh,downscript=./ifdown.sh,id=net0 \
	-append "root=/dev/vda rw console=ttyS0 earlycon=sbi"

$ cat ifup.sh
#!/bin/sh
brctl addif virbr0 $1
ifconfig $1 up

$ cat ifdown.sh
#!/bin/sh
ifconfig $1 down
brctl delif virbr0 $1

This brenchmark is vhost-net compare with virtio:

$ ./netperf -H <virbr0_ip> -l 100 -t TCP_STREAM

vhost-net:
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

131072  16384  16384    100.07    457.55

virtio:
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

131072  16384  16384    100.07    227.02


The next step is to support irqfd on RISC-V architecture.

Yifei Jiang (2):
  RISC-V: KVM: enable ioeventfd capability and compile for risc-v
  RISC-V: KVM: read\write kernel mmio device support

 arch/riscv/kvm/Kconfig     |  2 ++
 arch/riscv/kvm/Makefile    |  2 +-
 arch/riscv/kvm/vcpu_exit.c | 38 ++++++++++++++++++++++++++++++++------
 arch/riscv/kvm/vm.c        |  1 +
 4 files changed, 36 insertions(+), 7 deletions(-)

-- 
2.19.1