Re: [PATCH 2/3] KVM: Add gsi_msg_pending_bitmap for MSI-X

[Marcelo Tosatti <mtosatti@redhat.com>]

On Fri, Feb 13, 2009 at 11:37:45AM +0800, Sheng Yang wrote:
> > > +#define KVM_ASSIGNED_DEV_MSIX		((1 << 2) | (1 << 10))
> >
> > Can you explain the usage of the two bits?
> 
> Um... Just to keep consistent with formers(one for guest and one for host), at 
> cost of one bit.

OK

> > Can drop the printk's (also from find_gsi_from_host_irq).
> 
> Not that confident. In fact, I often triggered this during debug... IIRC, 
> userspace program shouldn't trigger this if kernel space works well. Maybe it 
> can be changed to WARN_ON() or BUG_ON() later.

OK

> > Check the return value?
> 
> Yeah...
> >
> > > +		enable_irq(irq);
> >
> > Do you guarantee that particular irq you're enable_irq'ing is not bogus?
> > Its has been passed from userspace after all.
> 
> It isn't passed from userspace. This one is filled by pci_enable_msix(), which 
> should be OK. 

Alright.

> > So you chose GSI == 0 as invalid because of x86 assumptions? Or is there
> > any other reason?
> 
> Yeah, it based on x86 and IA64 IRQ 0 can't be used by MSI-X. And only x86 
> support MSI-X now(and IA64 would follow later).

OK.

> >
> > IRQ sharing in the host side is not supported correct?
> 
> Um? Yeah... And seems we won't support it forever...

OK.