linux-kernel - Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes

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Message-ID: <20100402170515.GA32579@suse.de>
Date:	Fri, 2 Apr 2010 10:05:15 -0700
From:	Greg KH <gregkh@...e.de>
To:	Avi Kivity <avi@...hat.com>
Cc:	Tom Lyon <pugs@...n-about.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, "Hans J. Koch" <hjk@...utronix.de>
Subject: Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for
	non-privileged processes

On Fri, Apr 02, 2010 at 09:43:35AM +0300, Avi Kivity wrote:
> On 04/01/2010 10:24 PM, Tom Lyon wrote:
>>
>>> But there are multiple msi-x interrupts, how do you know which one
>>> triggered?
>>>      
>> You don't. This would suck for KVM, I guess, but we'd need major rework of the
>> generic UIO stuff to have a separate event channel for each MSI-X.
>>    
>
> Doesn't it suck for non-kvm in the same way?  Multiple vectors are there 
> for a reason.  For example, if you have a multiqueue NIC, you'd have to 
> process all queues instead of just the one that triggered.
>
>> For my purposes, collapsing all the MSI-Xs into one MSI-look-alike is fine,
>> because I'd be using MSI anyways if I could. The weird Intel 82599 VF only
>> supports MSI-X.
>>
>> So one big question is - do we expand the whole UIO framework for KVM
>> requirements, or do we split off either KVM or non-VM into a separate driver?
>> Hans or Greg - care to opine?
>>    
>
> Currently kvm does device assignment with its own code, I'd like to unify 
> it with uio, not split it off.
>
> Separate notifications for msi-x interrupts are just as useful for uio as 
> they are for kvm.

I agree, there should not be a difference here for KVM vs. the "normal"
version.

thanks,

greg k-h
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