[dpdk-dev] [PATCH v2 5/7] net/virtio_user: add vhost kernel support
jasowang at redhat.com
Mon Jan 9 05:51:11 CET 2017
On 2017年01月04日 15:22, Tan, Jianfeng wrote:
> Sorry, I forget to reply this comment.
> On 12/26/2016 3:44 PM, Yuanhan Liu wrote:
>>> + /* Does not work when VIRTIO_F_IOMMU_PLATFORM now, why? */
>> Because this feature need the vhost IOTLB support from the device
>> emulation. Patches for QEMU hasn't been merged yet, but it has been
>> there for a while.
> Yes. And it's in need of help from QEMU.
>> Since we don't have the support yet, for sure it won't work. But
>> I'm wondering why you have to disable it explicitly?
> Here we do not have QEMU. Frontend driver talks with vhost-net through
> virtio_user_dev. And both ends claim to support
> VIRTIO_F_IOMMU_PLATFORM. So this feature bit will be negotiated if we
> don't explicitly disable it. In my previous test, it fails in
> vhost_init_device_iotlb() of vhost kernel module.
Interesting, vhost_init_device_iotlb() only fail when OOM. Do you meet it?
> My guess is that, for this feature, without the help of QEMU, vhost
> kernel module cannot work independently.
Technically it can if your userspace supports device IOTLB APIs too.
Or if you're using static mappings, and preset all mappings through
VHOST_IOTLB_UPADATE to make sure no IOTLB misses.
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