RE: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface

[David Laight]

> Subject: Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface
> 
> On Wed, Sep 25, 2013 at 05:00:16PM -0400, Tejun Heo wrote:
> > Hello,
> >
> > On Wed, Sep 25, 2013 at 10:58:05PM +0200, Alexander Gordeev wrote:
> > > Unfortunately, pSeries is a shows-topper here :( It seems we have to
> > > introduce pci_get_msi{,x}_limit() interfaces to honour the quota
> > > thing.  I just hope the hardware set for pSeries is limited and we
> > > won't need to use it for all drivers.
> >
> > Can you please go into a bit of detail on that?  Why does it matter?
> 
> Because otherwise we will re-introduce a problem described by Michael:
> "We have a small number of MSIs available, limited by hardware &
> firmware, if we don't impose a quota then the first device that probes
> will get most/all of the MSIs and other devices miss out."

Would it be possible to do some kind of 2-stage allocation.
In the first pass the driver would pass a minimum and desired
number of MSI-X interrupts, but not actually be given any.
Interrupts could then be allocated after it is known how many
are required and how many are available.

	David



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