[Qemu OpenChannelSSD] Hello worl

• 命令行启动虚拟机,虚拟机内核需要是分支pblk.20分支pblk-lastest
  (git clone https://github.com/OpenChannelSSD/linux.git)

sudo qemu-system-x86_64 --enable-kvm -m 4G -smp 2 -hda ./VMs/vm1.raw -hdb ./VMs/vm1_1.raw -net nic -net tap \
-drive file=./VMs/blknvme.1,if=none,id=blknvme.1 \
-device nvme,drive=blknvme.1,serial=deadbeef,namespaces=1,lver=1,nlbaf=5,lba_index=3,mdts=10

• 其中nvme设备的参数(qemu_src/hw/block/nvme.c)

serial=deadbeef,
namespaces=1,  # namespaces=<int> : Namespaces to make out of the backing storage, Default:1
lver=1,        # lver=<int> : version of the LightNVM standard to use, Default:1
nlbaf=5,       # nlbaf=<int> : Number of logical block formats, Default:1
lba_index=3,   # lba_index=<int> : Default namespace block format index, Default:0
mdts=10        # mdts=<int> : Maximum data transfer size, Default:5

• nlbaf=5,lba_index=3据说这两个参数决定了nvme设备的块大小（block = 4K）,具体怎么处理的需要看Qemu中nvme设备的相关处理.
  （git clone https://github.com/OpenChannelSSD/qemu-nvme.git）

• 在虚拟机内可以见到一个nvme设备了.

work@vm1:~$ sudo nvme lnvm list
Number of devices: 1
Device          Block manager   Version
nvme0n1         none            (0,0,0)
work@vm1:~$ lsblk
NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sdb       8:16   0    30G  0 disk 
└─sdb1    8:17   0    30G  0 part /home/work/mnt/1
sr0      11:0    1  1024M  0 rom  
sda       8:0    0    20G  0 disk 
├─sda2    8:2    0   1.4G  0 part [SWAP]
└─sda1    8:1    0  18.6G  0 part /
nvme0n1 259:0    0    16G  0 disk 
work@vm1:~$ sudo nvme lnvm init -d nvme0n1
work@vm1:~$ sudo nvme lnvm list
Number of devices: 1
Device          Block manager   Version
nvme0n1         gennvm          (0,1,0)

• 紧接着在虚拟机中安装liblightnvm，以便用户态可以使用一些与OpenChannelSSD相关的api.就是去下这个githttps://github.com/OpenChannelSSD/liblightnvm，并make&&make install.

• 在虚拟机装好liblightnvm后，可以在用户态access一个OpenChannelSSD.
• hello_nvme.c:

#include <stdio.h>
#include <liblightnvm.h>
int main(int argc, char **argv)
{
    NVM_DEV dev = nvm_dev_open("/dev/nvme0n1");
    if (!dev) {
        perror("nvm_dev_open");
        return 1;
}
nvm_dev_pr(dev);
nvm_dev_close(dev);
return 0;

• 编译：（需要gcc版本 4.9.1以上）

 gcc hello_nvme.c -llightnvm -o hello_nvme

• 运行：

work@vm1:~/mnt/1/OpenChannelSSD/src/hello_nvme$ sudo ./hello_nvme 
dev { path(/dev/nvme0n1), name(nvme0n1), fd(3) }
dev-geo {
 nchannels(1), nluns(1), nplanes(1),
 nblocks(16352), npages(256), nsectors(1),
 page_nbytes(4096), sector_nbytes(4096), meta_nbytes(16),
 tbytes(17146314752b:16352Mb),
 vpg_nbytes(4096b:4Kb),
 vblk_nbytes(1048576b:1Mb)
}
dev-lba_map {
 channel_nbytes(17146314752)
 lun_nbytes(17146314752)
 plane_nbytes(4096)
 block_nbytes(1048576)
 page_nbytes(4096)
 sector_nbytes(4096)
}
dev-fmt {
 ch_ofz(20), ch_len(0),
 lun_ofz(20), lun_len(0),
 pl_ofz(20), pl_len(0),
 blk_ofz(0), blk_len(12),
 pg_ofz(12), pg_len(8),
 sec_ofz(20), sec_len(0)
}

• (补上一个模块关系简图)
  （http://openchannelssd.readthedocs.io/en/latest/）

• 过程中出了个问题.（感觉是需要OpenMP4.0）

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib/liblightnvm.so: undefined reference to `GOMP_parallel@GOMP_4.0'

看一下我的GCC版本

work@vm1:~/mnt/1/OpenChannelSSD/src/hello_nvme$ gcc --version
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

查一下这个GOMP是个所谓的多线程框架，gcc自带的，并且版本关系如下：

From GCC 4.2.0, OpenMP 2.5 is fully supported.
From GCC 4.4.0, OpenMP 3.0 is fully supported.
From GCC 4.7.0, OpenMP 3.1 is fully supported.
In GCC 4.9.0, OpenMP 4.0 is supported for C and C++, but not Fortran.
From GCC 4.9.1, OpenMP 4.0 is fully supported.

所以这里应该是gcc的版本不够.按照这个threadUbuntu 14.04 LTS 下升级 gcc 到 gcc-4.9、gcc-5 版本
装个gcc-4.9.
简要步骤如下：

1 sudo add-apt-repository ppa:ubuntu-toolchain-r/test
2 sudo apt-get update
3 sudo apt-get upgrade
4 sudo apt-get install gcc-4.9 g++-4.9

work@vm1:~/mnt/1/OpenChannelSSD/src/hello_nvme$ gcc-4.9 --version
gcc-4.9 (Ubuntu 4.9.4-2ubuntu1~14.04.1) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

再编译果然就OK.

• 与OpenchannelSSD相关项目

Linux Kernel Support (https://github.com/OpenChannelSSD/linux) Implements support for Open-Channel SSDs in the kernel. It is the core of identifying, managing, and using the Open-Channel SSDs.

liblightnvm Library (https://github.com/OpenChannelSSD/liblightnvm)A library that abstracts the underlying "raw" Open-Channel SSD device and provides abstractions such as append only, bad block management, etc.

General documentation (https://github.com/OpenChannelSSD/documentation)The documentation that is exposed through readthedocs.org

liblightnvm documentation (http://lightnvm.io/liblightnvm)The liblightnvm documentation

LightNVM Conditioning Tool (https://github.com/OpenChannelSSD/lnvm) Provides the lnvm-tool
cli management tool for verifying and conditioning Open-Channel SSDs.

LightNVM Test Tools (https://github.com/OpenChannelSSD/lightnvm-hw)Various tools to test kernel and target implementations.

QEMU with NVMe Open-Channel Support (https://github.com/OpenChannelSSD/qemu-nvme)Implements support for exposing a virtual open-channel SSD. Very useful for development.