netdev - Re: Unable to create more than 1 guest virtio-net device using vhost-net backend

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4BA5F59C.5070403@redhat.com>
Date:	Sun, 21 Mar 2010 12:31:56 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	Sridhar Samudrala <samudrala.sridhar@...il.com>,
	netdev <netdev@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: Unable to create more than 1 guest virtio-net device using vhost-net
 backend

On 03/21/2010 12:21 PM, Gleb Natapov wrote:
> On Sun, Mar 21, 2010 at 12:11:33PM +0200, Avi Kivity wrote:
>    
>> On 03/21/2010 11:55 AM, Michael S. Tsirkin wrote:
>>      
>>> On Fri, Mar 19, 2010 at 03:19:27PM -0700, Sridhar Samudrala wrote:
>>>        
>>>> When creating a guest with 2 virtio-net interfaces, i am running
>>>> into a issue causing the 2nd i/f falling back to userpace virtio
>>>> even when vhost is enabled.
>>>>
>>>> After some debugging, it turned out that KVM_IOEVENTFD ioctl()
>>>> call in qemu is failing with ENOSPC.
>>>> This is because of the NR_IOBUS_DEVS(6) limit in kvm_io_bus_register_dev()
>>>> routine in the host kernel.
>>>>
>>>> I think we need to increase this limit if we want to support multiple
>>>> network interfaces using vhost-net.
>>>> Is there an alternate solution?
>>>>
>>>> Thanks
>>>> Sridhar
>>>>          
>>> Nothing easy that I can see. Each device needs 2 of these.  Avi, Gleb,
>>> any objections to increasing the limit to say 16?  That would give us
>>> 5 more devices to the limit of 6 per guest.
>>>        
>> Increase it to 200, then.
>>
>>      
> Currently on each device read/write we iterate over all registered
> devices. This is not scalable.
>    

Yeah.  We need first to drop the callback based matching and replace it 
with explicit ranges, then to replace the search with a hash table for 
small ranges (keeping a linear search for large ranges, can happen for 
coalesced mmio).

-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html