On 2015/2/26 20:01, Michael S. Tsirkin wrote:
> On Thu, Feb 26, 2015 at 01:55:54PM +0200, Nikolay Nikolaev wrote:
>> On Thu, Feb 26, 2015 at 11:36 AM, Michael S. Tsirkin <m...@redhat.com> wrote:
>>>
>>> On Thu, Feb 26, 2015 at 09:30:40AM +0000, Gaohaifeng (A) wrote:
>>>> Hi
>>>>
>>>> I want to use pxe to install a guest os whose nic type is vhost user.
>>>> However
>>>> pxe rom doesn’t support msi-x interrupt, so qemu won’t start vhost net.
>>>>
>>>> Call relationship:
>>>>
>>>> virtio_net_vhost_status-> vhost_net_query-> vhost_dev_query->
>>>> virtio_pci_query_guest_notifiers -> msix_enabled
>>>>
>>>>
>>>>
>>>> In my test, I remove the msix check for vhost user interface and
>>>> successfully
>>>> install the guest os by pxe.
>>>>
>>>> Is it OK to do like this and will it cause other problems?
>>>>
>>>>
>>>>
>>>> Thanks.
>>>>
>>>> Haifeng Gao
>>>>
>>>
>>> I think we should fix it.
>>> As a quick hack, you should be able to just use vhostforce.
>>
>>
>> But isn't that what vhostforce is for, runnign vhost with non
>> MSI-enabled guests?
>>
>> regards,
>> Nikolay Nikolaev
>
> It isn't really.
>
> kernel vhost is more or less an optimization. since it performs
> slowly for non msi guests, it turns itself off for them by default,
> and you fall back to virtio in qemu which for non msi seems to be
> faster. to re-enable, set force to on.
>
> vhost user doesn't work with virtio in qemu, it should
> ignore vhostforce and just handle non msix guests.
If I understand correctly (if not,pls correct me), We can ignore vhostforce
value and set it to true. So even non msix can use vhost user nic.
code like this:
--- vhost-user.c
+++ vhost-user.c
@@ -230,7 +230,6 @@
{
const NetdevVhostUserOptions *vhost_user_opts;
CharDriverState *chr;
- bool vhostforce;
assert(opts->kind == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
vhost_user_opts = opts->vhost_user;
@@ -247,12 +247,6 @@
return -1;
}
- /* vhostforce for non-MSIX */
- if (vhost_user_opts->has_vhostforce) {
- vhostforce = vhost_user_opts->vhostforce;
- } else {
- vhostforce = false;
- }
- return net_vhost_user_init(peer, "vhost_user", name, chr, vhostforce);
+ return net_vhost_user_init(peer, "vhost_user", name, chr, true);
}
>
>
>
>>>
>>>
>>> --
>>> MST
>>>
>
> .
>
