Re: [Qemu-devel] [PATCH] ivshmem: Store file descriptor for vhost-user negotiation

[Tetsuya Mukawa]

2015-12-07 20:31 GMT+09:00 Marc-André Lureau <address@hidden>:
> Hi
>
> On Fri, Dec 4, 2015 at 3:55 PM, Tetsuya Mukawa <address@hidden> wrote:
>>> What's the use case or test case?
>>
>> One of example is userspace device driver like DPDK PMD.
>> Actually, I've found this fd related behavior using DPDK virtio-net PMD.
>> Could you please check below to know my use case more?
>> http://thread.gmane.org/gmane.comp.networking.dpdk.devel/28467/focus=28493
>
> Thanks. Why not use memory-backend-file with share=on ?

Thanks for commenting.
I guess you suggest me to use memory-backend file as guest main memory.
Is this correct?
If so, it might not work because first 1MB of QEMU main memory is
reserved by others like BIOS.
To work it with DPDK process, I may need to to fix DPDK memory
management not to use first 1MB.

> I think I understand you want to use the same BAR address as the host shared
> memory location to avoid extra offset computation. I don't know about
> the limitations here. Is this extra offset really worth saving?

Yes, I don't need to change DPDK virtio-net PMD a lot, because a
physical memory region that virtio-net PMD on host uses can be valid
and has same physical memory address in QEMU guest.
This is the trick I can use almost same virtio-net driver on guest and host.

Tetsuya,

> Finally, I wonder what qemu is really doing in the end ;)
>
> Michael, could you comment about this vhost-user use case? (see above
> linked thread)
>
>
> --
> Marc-André Lureau