linux-kernel - Re: [PATCH for-2.6.35] virtio-pci: disable msi at startup

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Message-ID: <20100623144307.GB30526@redhat.com>
Date:	Wed, 23 Jun 2010 17:43:08 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	virtualization@...ts.linux-foundation.org,
	Anthony Liguori <aliguori@...ibm.com>,
	linux-pci@...r.kernel.org, Matt Carlson <mcarlson@...adcom.com>,
	linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Bjorn Helgaas <bjorn.helgaas@...com>
Subject: Re: [PATCH for-2.6.35] virtio-pci: disable msi at startup

On Wed, Jun 23, 2010 at 05:21:37PM +0300, Avi Kivity wrote:
> On 06/23/2010 04:59 PM, Michael S. Tsirkin wrote:
>>
>>> Why doesn't a device reset result in msi being cleared?
>>>      
>> This is not a standard function reset. This is virtio specific
>> command. So it only clears virtio registers.
>>    
>
> I see.  We should implement FLR in qemu.

We can do this. Or PM reset. however ...

>  If we don't already do so, we  
> should probably FLR anything that moves when a kexec kernel starts.

Probably only whatever we want to use. But whether this will make it
more, or less robust, is an open question.

>>> Shouldn't a reset be equivalent to power cycling?
>>>      
>> If we did this, driver would need to restore registers
>> such as BAR etc.
>>    
>
> We could save/restore the registers we care about.

It seems easier to clear registers we care about.  It's also too late
now: changing behaviour will break old drivers.

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