linux-kernel - Re: Regression with commit f9cde5f in 2.6.30-gitX

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Message-ID: <20090624192813.GF7239@us.ibm.com>
Date:	Wed, 24 Jun 2009 12:28:13 -0700
From:	Gary Hade <garyhade@...ibm.com>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	Gary Hade <garyhade@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Larry Finger <Larry.Finger@...inger.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	x86 maintainers <x86@...nel.org>, Len Brown <lenb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Regression with commit f9cde5f in 2.6.30-gitX

On Wed, Jun 24, 2009 at 10:03:39PM +0530, Jaswinder Singh Rajput wrote:
> On Wed, 2009-06-24 at 09:13 -0700, Gary Hade wrote:
> > On Wed, Jun 24, 2009 at 09:27:48PM +0530, Jaswinder Singh Rajput wrote:
> > > On Wed, 2009-06-24 at 17:19 +0200, Thomas Gleixner wrote:
> > > > Larry,
> > > > 
> > > > On Wed, 24 Jun 2009, Larry Finger wrote:
> > > > > For the record, the printout from the patch results in the following:
> > > > > 
> > > > > PCI: Failed to allocate 0xd0000-0xd3fff from PCI mem for PCI Bus 0000:00
> > > > > PCI: Failed to allocate 0xec000-0xeffff from PCI mem for PCI Bus
> > > > > 0000:00 due to _CRS returning more than 13 resource descriptors
> > > > > PCI: Failed to allocate 0xf0000-0xfffff from PCI mem for PCI Bus
> > > > > 0000:00 due to _CRS returning more than 13 resource descriptors
> > > > > PCI: Failed to allocate 0xc0000000-0xfebfffff from PCI mem for PCI Bus
> > > > > 0000:00 due to _CRS returning more than 13 resource descriptors
> > > > 
> > > > can you please the patch below instead of the other one ?
> > > > 
> > > > Thanks,
> > > > 
> > > > 	tglx
> > > > ---
> > > > diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> > > > index 16c3fda..39a0cce 100644
> > > > --- a/arch/x86/pci/acpi.c
> > > > +++ b/arch/x86/pci/acpi.c
> > > > @@ -99,7 +99,6 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > > >  			"%d resource descriptors\n", (unsigned long) res->start,
> > > >  			(unsigned long) res->end, root->name, info->name,
> > > >  			max_root_bus_resources);
> > > > -		info->res_num++;
> > > >  		return AE_OK;
> > > >  	}
> > > >  
> > > 
> > > This fails and system does not boot, I already tested this patch 8 hours
> > > ago.
> > 
> > I think the resource array needs to be larger.  Can you try
> > the below patch?
> > 
> > Gary
> > 
> > --- linux-2.6.30-rc8/include/linux/pci.h.ORIG	2009-06-24 09:03:41.000000000 -0700
> > +++ linux-2.6.30-rc8/include/linux/pci.h	2009-06-24 09:06:50.000000000 -0700
> > @@ -319,7 +319,7 @@ static inline void pci_add_saved_cap(str
> >  }
> >  
> >  #ifndef PCI_BUS_NUM_RESOURCES
> > -#define PCI_BUS_NUM_RESOURCES	16
> > +#define PCI_BUS_NUM_RESOURCES	20
> >  #endif
> >  
> >  #define PCI_REGION_FLAG_MASK	0x0fU	/* These bits of resource flags tell us the PCI region flags */
> 
> 
> Larry already suggested PCI_BUS_NUM_RESOURCES to 24 in his patch (check
> first reply from him).

Sorry I missed that.

> 
> Then what is the point of removing last 3 and then adding 3 or more
> resources, so patch f9cde5f lost its purpose,

The reason for not populating the last 3 slots of the resource
array when there is a transparent bridge on the bus is to make
sure devices downstream of the transparent bridge get the resources
they need.  Because of the offset of 3 between the transparent
bridge parent and child bus resource arrays established by
	if (dev->transparent) {
		dev_info(&dev->dev, "transparent bridge\n");
		for(i = 3; i < PCI_BUS_NUM_RESOURCES; i++)
			child->resource[i] = child->parent->resource[i - 3];
	}
in pci_read_bridge_bases() [drivers/pci/probe.c] and refreshed by
similar in adjust_transparent_bridge_resources() [arch/x86/pci/acpi.c]
the transparent bridge child bus resource array will not reference
the resources in those last 3 slots.

> best case will be to
> revert f9cde5f as it also removed :
> 
> if (info->res_num >= PCI_BUS_NUM_RESOURCES)
>                 return AE_OK;
> 
> which is required in any case.

In the case of a root bus without a transparent bridge,
this still exists (w/added warning and resource count increment) as
	if (info->res_num >= max_root_bus_resources) {
		< warn and increment resource count >
		return AE_OK;
	}
because max_root_bus_resources==PCI_BUS_NUM_RESOURCES

In the case were there is a transparent bridge on the root bus,
'max_root_bus_resources' needs to be 3 less than PCI_BUS_NUM_RESOURCES
to avoid populating the last 3 slots of the array that are not
visible below the transparent bridge.

Gary

-- 
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503  IBM T/L: 775-4503
garyhade@...ibm.com
http://www.ibm.com/linux/ltc

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