Vladimir Sementsov-Ogievskiy <[email protected]> writes:
> On 16.10.25 11:48, Markus Armbruster wrote:
>> Vladimir Sementsov-Ogievskiy <[email protected]> writes:
>>
>>> This option for tap and vhost-user netdevs doesn't make sense
>>> since long ago (10 years!), starting from commits:
>>>
>>> 1e7398a140f7a6 ("vhost: enable vhost without without MSI-X")
>>> 24f938a682d934 ("vhost user:support vhost user nic for non msi guests")
>>>
>>> Prior these commits, to enable kernel vhost-net, or vhost-user-net for
>>> some specific kind of guests (that don't have MSI-X support), you should
>>> have set vhostforce=on.
>>>
>>> Now guest type doesn't matter, all guests are equal for these
>>> options logic.
>>>
>>> For tap the current logic is:
>>> vhost=on / vhost=off : vhostforce ignored, doesn't make sense
>>> vhost unset : vhostforce counts, enabling vhost
>>>
>>> So you may enable vhost for tap several ways:
>>> - vhost=on
>>> - vhostforce=on
>>> - vhost=on + vhostforce=on
>>> - and even vhost=on + vhostforce=off
>>>
>>> - they are all equal.
>>>
>>> For vhost-user we simply ignore the vhostforce option at all in the
>>> code.
>>>
>>> Let's finally deprecate the extra options.
>>>
>>> Also, fix @vhostforce documentation everywhere to show the real picture,
>>> and update vhost-user test to not use deprecated option.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
[...]
>>> diff --git a/qemu-options.hx b/qemu-options.hx
>>> index 0223ceffeb..35a70096e8 100644
>>> --- a/qemu-options.hx
>>> +++ b/qemu-options.hx
>>> @@ -2882,7 +2882,7 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
>>> #else
>>> "-netdev
>>> tap,id=str[,fd=h][,fds=x:y:...:z][,ifname=name][,script=file][,downscript=dfile]\n"
>>> "
>>> [,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]\n"
>>> - "
>>> [,vhostfd=h][,vhostfds=x:y:...:z][,vhostforce=on|off][,queues=n]\n"
>>> + " [,vhostfd=h][,vhostfds=x:y:...:z][,queues=n]\n"
>>> " [,poll-us=n]\n"
>>> " configure a host TAP network backend with ID 'str'\n"
>>> " connected to a bridge (default="
>>> DEFAULT_BRIDGE_INTERFACE ")\n"
>>> @@ -2898,9 +2898,7 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
>>> " default is disabled 'sndbuf=0' to enable flow control
>>> set 'sndbuf=1048576')\n"
>>> " use vnet_hdr=off to avoid enabling the IFF_VNET_HDR
>>> tap flag\n"
>>> " use vnet_hdr=on to make the lack of IFF_VNET_HDR
>>> support an error condition\n"
>>> - " use vhost=on to enable experimental in kernel
>>> accelerator\n"
>>> - " (only has effect for virtio guests which use
>>> MSIX)\n"
>>> - " use vhostforce=on to force vhost on for non-MSIX
>>> virtio guests\n"
>>> + " use vhost=on to enable in kernel accelerator\n"
>>
>> So the kernel's accelerator is no longer experimental?
>
> Reading this, I heard the first time that vhost-net is experimental.
> It's about 15 years old, and used in production. I think "experimental"
> is inappropriate word here)
Just double-checking :)
The text you adjust is from 2010 (commit 82b0d80ef6a). I guess the
accelerator was experimental back then.
Mention the correction in the commit message?
[...]
