Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device driver

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device driver
Date	2015-11-04 16:20 +0100
Message-ID	<qr80V-28m-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <qogo2-84h-23@gated-at.bofh.it> <qqsbo-hk-17@gated-at.bofh.it> <qqxup-3IW-11@gated-at.bofh.it> <qqIg9-2a9-3@gated-at.bofh.it> <qr7xU-1HX-19@gated-at.bofh.it>
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On Wed, 4 Nov 2015, Keith Busch wrote:

> On Tue, Nov 03, 2015 at 12:42:02PM +0100, Thomas Gleixner wrote:
> > On Tue, 3 Nov 2015, Keith Busch wrote:
> > > > > +	msi_irqdomain = pci_msi_create_irq_domain(NULL, &pci_chained_msi_domain_info,
> > > > > +						  vmd_irqdomain);
> > 
> > But that parent limitation does not matter simply because your
> > msi_irqdomain does not follow down the hierarchy in the allocation
> > path.
> > 
> > So we can avoid the vmd_irqdomain creation completely. It's just
> > wasting memory and has no value at all. Creating the msi domain with a
> > NULL parent is possible.
> 
> I'm having trouble following the hierarchy and didn't understand the
> connection between the parent and msi comain. It's still new to me,
> but I don't think a NULL parent is allowable with msi domains:
> 
>  pci_msi_setup_msi_irqs()
>   pci_msi_domain_alloc_irqs()
>    msi_domain_alloc_irqs()
>     __irq_domain_alloc_irqs()
>      irq_domain_alloc_irqs_recursive()
>       msi_domain_alloc()
>        irq_domain_alloc_irqs_parent()
> 
> The last call returns -ENOSYS since there parent is NULL. Was the
> intension to allow no parent, or do I still need to allocate one to
> achieve the desired chaining?

Hmm, seems I missed that part. But that's a fixable problem. Jiang?

Thanks,

	tglx
 
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Thread

Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Thomas Gleixner <tglx@linutronix.de> - 2015-11-02 19:40 +0100
  Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Keith Busch <keith.busch@intel.com> - 2015-11-03 01:20 +0100
    Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Thomas Gleixner <tglx@linutronix.de> - 2015-11-03 12:50 +0100
      Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Keith Busch <keith.busch@intel.com> - 2015-11-04 15:50 +0100
        Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Thomas Gleixner <tglx@linutronix.de> - 2015-11-04 16:20 +0100
          Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Jiang Liu <jiang.liu@linux.intel.com> - 2015-11-05 07:40 +0100
            Re: [RFC PATCHv3 3/4] x86/pci: Initial commit for new VMD device  driver Keith Busch <keith.busch@intel.com> - 2015-11-05 16:00 +0100

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