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

[Avi Kivity]

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

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