diff mbox

[Question] about vhost user Interface

Message ID 54F02F14.5040802@huawei.com
State New
Headers show

Commit Message

gaohaifeng Feb. 27, 2015, 8:47 a.m. UTC 
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 <mst@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:



> 
> 
> 
>>>
>>>
>>> --
>>> MST
>>>
> 
> .
>
diff mbox

Patch

--- 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);
 }