From: Ram Pai <linuxram@us.ibm.com>
To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Ram Pai <linuxram@us.ibm.com>,
Bjorn Helgaas <bjorn.helgaas@hp.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
clemens@ladisch.de, Yinghai Lu <yinghai@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
peter.henriksson@gmail.com, ebiederm@aristanetworks.com
Subject: Re: [PATCH 1/1] PCI: ignore failure to preallocate minimal resources to hotplug bridges
Date: Tue, 11 Jan 2011 13:10:22 -0800 [thread overview]
Message-ID: <20110111211021.GA26352@ram-laptop> (raw)
In-Reply-To: <20110107143208.036a3c01@jbarnes-desktop>
On Fri, Jan 07, 2011 at 02:32:08PM -0800, Jesse Barnes wrote:
> On Fri, 22 Oct 2010 10:16:40 -0700
> Ram Pai <linuxram@us.ibm.com> wrote:
>
> > PCI: ignore failure to preallocate minimal resources to
> > hotplug bridges
> >
> > Linux tries to pre-allocate minimal resources to hotplug
> > bridges. This works fine as long as there are enough
> > resources to satisfy all other genuine resource
> > requirements. However if enough resources are not
> > available to satisfy the pre-allocation, the
> > resource-allocator reports errors and returns failure.
> >
> > This patch distinguishes between must-need resources and
> > nice-to-have resources. Any failure to allocate
> > nice-to-have resources are ignored.
> >
> > This behavior can be particularly useful to trigger
> > automatic reallocation, if the OS discovers genuine
> > resource allocation conflicts or genuine unallocated
> > BARs caused by not-so-smart allocation behavior of the
> > native BIOS.
> >
> > The motivation for this patch is due a issue reported in
> > https://bugzilla.kernel.org/show_bug.cgi?id=15960
> >
> > Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> >
>
> Seems like we want a fix like this; did you see Bjorn's comments?
> Maybe we can adjust the order of allocation instead?
>
> What issues do you still have outstanding wrt resource allocation? Do
> you still think you need the big "reallocate everything" option?
Jesse,
Yes I saw Bjorn's comment but then i got pulled into something else and
made no progress. Just yesterday I started looking into this and co-incidently
see your mail too.
I am not sure how to order the allocation given the current organization
of the code.
The real problem is that the kernel wants to pre-allocate some minimum
memory and ioport to hotplug bridges. On a system with just enough resources to
satisfy the currently installed devices, the current code organization makes it
hard to organize the allocation order such that atleast the must-have requests
are satisfied.
An ideal solution should first satisfy the must-have requests and if
any additional resources are still available then pre-allocate nice-to-have
requests.
I am thinking of structuring the code the following way.
a) note down the must-have requirement as well as the nice-to-way requirement
for each pci-resource.
b) run through each resource and satisfy the must-have requirement.
c) if (b) succeeds, run through each resource and *try* to satisfy the
nice-to-way requirement.
The other solution is to simply ignore preallocation to hotplug bridges.
Please suggest,
RP
>
> Thanks,
> --
> Jesse Barnes, Intel Open Source Technology Center
--
Ram Pai
System X Device-Driver Enablement Lead
Linux Technology Center
Beaverton OR-97006
503-5783752 t/l 7753752
linuxram@us.ibm.com
next prev parent reply other threads:[~2011-01-11 21:10 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-06 22:58 [RFC v2 PATCH 1/1] PCI: override BIOS/firmware resource allocation Ram Pai
2010-10-06 23:39 ` Bjorn Helgaas
2010-10-07 0:30 ` Ram Pai
2010-10-07 4:13 ` Bjorn Helgaas
2010-10-07 20:42 ` Ram Pai
2010-10-07 21:41 ` Bjorn Helgaas
2010-10-08 17:32 ` Ram Pai
2010-10-08 20:16 ` Bjorn Helgaas
2010-10-12 7:05 ` Ram Pai
2010-10-12 19:01 ` Bjorn Helgaas
2010-10-18 20:10 ` Jesse Barnes
2010-10-19 17:17 ` Ram Pai
2010-10-19 18:24 ` Jesse Barnes
2010-10-22 0:28 ` Ram Pai
2010-10-22 17:55 ` Bjorn Helgaas
2010-10-22 18:59 ` Ram Pai
2010-10-22 21:49 ` Bjorn Helgaas
2010-10-22 17:16 ` [PATCH 1/1] PCI: ignore failure to preallocate minimal resources to hotplug bridges Ram Pai
2010-10-22 22:16 ` Bjorn Helgaas
2011-01-07 22:32 ` Jesse Barnes
2011-01-11 21:10 ` Ram Pai [this message]
2011-01-14 18:19 ` [PATCH 1/1] PCI: allocate essential resources before reserving hotplug resources Ram Pai
2011-01-18 20:52 ` Bjorn Helgaas
2011-01-18 21:42 ` Ram Pai
2011-01-18 22:11 ` Bjorn Helgaas
2011-01-19 19:58 ` [PATCH 1/1 v3] " Ram Pai
2011-01-20 1:00 ` [PATCH 1/1 v4] " Ram Pai
2011-01-21 1:22 ` Yinghai Lu
2011-01-21 7:17 ` Ram Pai
2011-01-18 21:30 ` [PATCH 1/1 Version 2.0] " Ram Pai
2011-01-18 21:46 ` Bjorn Helgaas
2011-01-18 22:03 ` Ram Pai
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