Subject: Re: [PULL 2/2] vhost: replace rcu with mutex

From: Vlad Yasevich <[email-masked]>
Date: Tue, 03 Jun 2014 09:35:17 -0400

On 06/03/2014 08:48 AM, Paolo Bonzini wrote:
> Il 02/06/2014 23:58, Eric Dumazet ha scritto:
>> This looks dubious
>>
>> What about using kfree_rcu() instead ?
> 
> It would lead to unbound allocation from userspace.
> 
>> translate_desc() still uses rcu_read_lock(), its not clear if the mutex
>> is really held.
> 
> Yes, vhost_get_vq_desc must be called with the vq mutex held.
> 
> The rcu_read_lock/unlock in translate_desc is unnecessary.
> 

If that's true, then does dev->memory really needs to be rcu protected?
It appears to always be read under mutex.

-vlad

> Paolo
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