Re: [PATCH] I/O space boot parameter

[Daniel Yeisley <dan.yeisley@unisys.com>]

On Tue, 2007-03-20 at 13:26 -0700, Greg KH wrote:
> On Tue, Mar 20, 2007 at 01:25:38PM -0400, Daniel Yeisley wrote:
> > On Tue, 2007-03-20 at 11:00 -0700, Greg KH wrote:
> > > On Tue, Mar 20, 2007 at 12:18:24PM -0400, Daniel Yeisley wrote:
> > > > It has been mentioned before that large systems with a lot of PCI buses
> > > > have issues with the 64k I/O space limit.  The ES7000 has a BIOS option
> > > > to either assign I/O space to all adapters, or only to those that need
> > > > it.  A list of supported adapters that don't need it is kept in the
> > > > BIOS.  When this option is used, the kernel sees the BARs on the
> > > > adapters and still tries to assign I/O space (until it runs out).  I've
> > > > written a patch to implement a boot parameter that tells the kernel not
> > > > to assign I/O space if the BIOS hasn't.  
> > > 
> > > How prelevant are machines like this?  And why are the BARs on these
> > > devices wrong?
> > > 
> > I don't have any sales numbers, but I can tell you that our current
> > systems can have up to 64 PCI buses.  
> > 
> > I've been working with Emulex cards, and my understanding is that the
> > BARs on the devices aren't wrong, but we can't allocate 4k of I/O space
> > for each one.  So we maintain a list in the BIOS of devices that don't
> > actually need I/O space and then don't assign it.  I've tested an a
> > x86_64 system with 20+ adapters and saw all the disks attached without
> > any problems.
> 
> Ah.  Others are working on providing a fix for this too, but it is being
> done in the drivers themselves, not in the pci core.  Look in the
> linux-pci mailing list archives for those patches (I don't think they
> every went into mainline for some reason, but I might be wrong...)
> 
> I suggest you work with those developers, as they have the same issue
> that you are trying to solve here.
> 

I have seen some patches that make the drivers I/O port free here:
http://lkml.org/lkml/2006/2/26/261

I checked and they still aren't in the mainline.  

I don't know that it matters though because I see all the disks attached
to the system regardless of whether or not the adapters get I/O space.
The real issue I have is with all the error messages I get at boot.  I
see 40+ messages that say "PCI: Failed to allocate I/O
resource..." (from setup-res.c) when the kernel tries to allocate the
I/O space and can't.  The modules load fine.  I see all the disks just
fine.  But that many error messages tends to raise concerns and causes
support calls from customers.

Dan