Re: Remaining passthrough/VT-d tasks list

["Yang, Sheng" <sheng.yang@intel.com>]

On Sunday 28 September 2008 13:04:06 Avi Kivity wrote:
> Tian, Kevin wrote:
> >> No. Maybe the Neocleus polarity trick (which also reduces performance).
> >
> > To my knowledge, Neocleus polarity trick can't solve this isolation
> > issue, which just provides one effecient way to track
> > assertion/deassertion transition on the irq line. For example, reverse
> > polarity when receiving an instance, and then a new irq instance would
> > occur when all devices de- assert on shared irq line, and then recover
> > the polarity. In your concerned case where guest driver misbehaves, this
> > polarity trick can't work neither as one device always asserts the line.
>
> You're right, I didn't think it through.
>
> If there was a standard way to mask pci irqs, it might have worked, but
> there isn't, unfortunately.
>
What if we got a way to mask pci irqs? We also have to unmask pci irq when 
guest wrote EOI to vlapic(or at any other time). I think this still cause 
problem. The problem is, we don't know if guest would deassert the line. 
Maybe add some time-based detection here might work?

And about the mask of pci irq, how about disable PCI device interrupt using 
Device Control Register bit 10? Not sure if it would affect the pending 
transaction, also not sure all device support this (though they should 
support).

--
regards
Yang, Sheng