> -----Original Message----- > From: Linhaifeng [mailto:haifeng.lin at huawei.com] > Sent: Thursday, November 13, 2014 7:24 PM > To: Xie, Huawei; 'Tetsuya Mukawa'; dev at dpdk.org; lilijun; zhangkun > Subject: Re: [dpdk-dev] vhost-user technical isssues > > > > On 2014/11/14 9:28, Xie, Huawei wrote: > > > > > >> -----Original Message----- > >> From: Linhaifeng [mailto:haifeng.lin at huawei.com] > >> Sent: Wednesday, November 12, 2014 11:28 PM > >> To: Xie, Huawei; 'Tetsuya Mukawa'; dev at dpdk.org > >> Subject: Re: [dpdk-dev] vhost-user technical isssues > >> > >> > >> > >> On 2014/11/12 5:37, Xie, Huawei wrote: > >>> Hi Tetsuya: > >>> There are two major technical issues in my mind for vhost-user > >> implementation. > >>> > >>> 1) memory region map > >>> Vhost-user passes us file fd and offset for each memory region. > Unfortunately > >> the mmap offset is "very" wrong. I discovered this issue long time ago, and > also > >> found > >>> that I couldn't mmap the huge page file even with correct offset(need > double > >> check). > >>> Just now I find that people reported this issue on Nov 3. > >>> [Qemu-devel] [PULL 27/29] vhost-user: fix mmap offset calculation > >>> Anyway, I turned to the same idea used in our DPDK vhost-cuse: only use > >>> the > fd > >> for region(0) to map the whole file. > >>> I think we should use this way temporarily to support qemu-2.1 as it has > >>> that > >> bug. > >>> > >> > >> the size of region 0 is not same as the file size. may be you should mmap > >> the > >> other region. > > Haifeng: > > > > Will calculate the maximum memory size, and use any file fd to mmap it. > > Here we assume the fds for different regions actually point to the same > > file. > > actually there may be two hugepage files created by qemu. > one day i create a 4G VM found qemu create 2 hugepage file and send them to > vhost-user. > you can try to test it. Ok, if that is the case, we need to fix vhost-cuse as well.
> > > > > In theory we should use the fd for each region to map each memory region. > > In fact we could map once. This will also save address space for 1GB huge > > page > > due to mmap alignment requirement. > >> > >> region 0: > >> gpa = 0x0 > >> size = 655360 > >> ua = 0x2aaaaac00000 > >> offset = 0 > >> > >> region 1:// use this region to mmap.BTW how to avoid mmap twice when > there > >> are two devices? > >> gpa = 0xC0000 > >> size = 2146697216 > >> ua = 0x2aaaaacc0000 > >> offset = 786432 > > > > What do you mean by two devices? > >> > >> > > e.g there are two vhost-user backends in a VM, we will receive two > SET_MEM_TABLE messages, actually we only need mmap once in one message. > > I think qemu should add a new message to send all hugepage fd and size once. > as this we not need to mmap and calculate memory in set_mem_table message. > > >> > >>> 2) what message is the indicator for vhost start/release? > >>> Previously for vhost-cuse, it has SET_BACKEND message. > >>> What we should do for vhost-user? > >>> SET_VRING_KICK for start? > >>> What about for release? > >>> Unlike the kernel virtio, the DPDK virtio in guest could be restarted. > >>> > >>> Thoughts? > >>> > >>> -huawei > >>> > >>> > >> > >> -- > >> Regards, > >> Haifeng > > > > > > . > > > > -- > Regards, > Haifeng
