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

[Avi Kivity <avi@redhat.com>]

On 06/23/2010 06:26 PM, Michael S. Tsirkin wrote:
>
>
>>>
>>>        
>>>>>> 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.
>>>        
>> We know the registers we care about, we don't know the ones we don't.
>>      
> If/when we use more registers, we can update driver to clear them on start.
>    

The kdump kernel may not load drivers for those extra devices.

>> I'm talking about FLRing all cards, not just those you want to use.
>>      
> reset using FLR/PM is complex because of the need to save/restore
> config space. Doing this on a crashing kernel sounds scary.
>    

Well, you only need to save/restore for the devices you use.  The rest 
you reset and forget.

I don't really see why copying some config space is crazy.

>>>     It's also too late
>>> now: changing behaviour will break old drivers.
>>>
>>>        
>> Why?  the FLR is triggered by the guest kernel, so all drivers will be
>> aware it was FLRed.
>>      
> Not for FLR. Too late to reset on PA write.
>
>    

What's PA write?

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