Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation

[Peter Xu <peterx@redhat.com>]

On Fri, Jan 20, 2017 at 09:15:27AM +0000, Tian, Kevin wrote:
> > From: Peter Xu [mailto:peterx@redhat.com]
> > Sent: Friday, January 20, 2017 5:05 PM
> > 
> > On Fri, Jan 20, 2017 at 08:22:14AM +0000, Tian, Kevin wrote:
> > > > From: Peter Xu [mailto:peterx@redhat.com]
> > > > Sent: Friday, January 13, 2017 11:06 AM
> > > >
> > > > Before we have int-remap, we need to bypass interrupt write requests.
> > > > That's not necessary now - we have supported int-remap, and all the irq
> > > > region requests should be redirected there. Cleaning up the block with
> > > > an assertion instead.
> > >
> > > This comment is not accurate. According to code, the reason why you
> > > can do such simplification is because we have standalone memory
> > > region now for interrupt addresses. There should be nothing to do
> > > with int-remap, which can be disabled by guest... Maybe the standalone
> > > region was added when developing int-remap, but functionally they
> > > are not related. :-)
> > 
> > IMHO the above commit message is fairly clear. :-)
> > 
> > But sure I can add some more emphasise like:
> > 
> >   "Before we have int-remap memory region, ..."
> > 
> > Do you think it's okay? Or any better suggestion?
> > 
> > (Just to mention that even guest disables IR, the MSI region will
> >  still be there.)
> > 
> 
> My option is simple - this patch has nothing to do with int-remap.
> It's not necessary, not because we supported int-remap. It's because
> we have a standalone memory region for interrupt addresses, as you
> described in the code. :-)

I really think they are the same thing...

How about this:

    Now we have a standalone memory region for MSI, all the irq region
    requests should be redirected there. Cleaning up the block with an
    assertion instead.

-- peterx