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

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Message-ID: <4BB59217.90102@redhat.com>
Date:	Fri, 02 Apr 2010 09:43:35 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Tom Lyon <pugs@...n-about.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Hans J. Koch" <hjk@...utronix.de>, gregkh@...e.de
Subject: Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged
 processes

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.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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