On 1/6/2016 11:57 AM, Tetsuya Mukawa wrote: > On 2015/12/28 20:06, Tetsuya Mukawa wrote: >> On 2015/12/24 23:05, Tan, Jianfeng wrote: >>> Hi Tetsuya, >>> >>> After several days' studying your patch, I have some questions as follows: >>> >>> 1. Is physically-contig memory really necessary? >>> This is a too strong requirement IMHO. IVSHMEM doesn't require this in its >>> original meaning. So how do you think of >>> Huawei Xie's idea of using virtual address for address translation? (In >>> addition, virtual address of mem_table could be >>> different in application and QTest, but this can be addressed because >>> SET_MEM_TABLE msg will be intercepted by >>> QTest) >> Hi Jianfeng, >> >> Thanks for your suggestion. >> Huawei's idea may solve contig-mem restriction. >> Let me have time to check it more. > Hi Jianfeng, > > I made sure we can remove the restriction with Huawei's idea. > One thing I concern is below. > If we don't use contiguous memory, this PMD will not work with other > 'physical' PMDs like e1000 PMD, virtio-net PMD, and etc. > (This is because allocated memory may not be physically contiguous.) > > One of examples is that if we implement like above, in QEMU guest, we > can handle a host NIC directly, but in container, we will not be able to > handle the device. > This will be a restriction for this virtual addressing changing. > > Do you know an use case that the user wants to handle 'physical' PMD and > 'virtual' virtio-net PMD together? > > Tetsuya, Hi Tetsuya,
I have no use case in hand, which handles 'physical' PMDs and 'virtual' virtio-net PMD together. (Pavel Fedin once tried to run ovs in container, but that case just uses virtual virtio devices, I don't know if he has plan to add 'physical' PMDs as well.) Actually, it's not completely contradictory to make them work together. Like this: a. containers with root privilege We can initialize memory as legacy way. (TODO: besides physical-contiguous, we try allocate virtual-contiguous big area for all memsegs as well.) a.1 For vhost-net, before sending memory regions into kernel, we can merge those virtual-contiguous regions into one region. a.2 For vhost-user, we can merge memory regions in the vhost. The blocker is that for now, maximum fd num was restricted by VHOST_MEMORY_MAX_NREGIONS=8 (so in 2M-hugepage's case, 16M shared memory is not nearly enough). b. containers without root privilege No need to worry about this problem, because it lacks of privilege to construct physical-contiguous memory. Thanks, Jianfeng
