linux-kernel - RE: SR-IOV enabling process failed in kernel 2.6.32

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Message-ID: <2ED289D4E09FBD4D92D911E869B97FDD01E6E555@mtlexch01.mtl.com>
Date:	Tue, 8 Dec 2009 11:07:57 +0200
From:	"Erez Shitrit" <erezsh@...lanox.co.il>
To:	<gregkh@...e.de>
Cc:	<linux-kernel@...r.kernel.org>,
	<linux-pci@...ey.karlin.mff.cuni.cz>,
	"Erez Shitrit" <erezsh@...lanox.co.il>
Subject: RE: SR-IOV enabling process failed in kernel 2.6.32

Hi Greg,

We are working on InfiniBand device that supports SR-IOV.
and lately (from version 2.6.32 ) we faced a problem:
When the driver tried to enable SR-IOV it failed to allocate resources
for the 2 BARS the device needs.
The situation is when there are 2 BARS, the first asks for little amount
of memory and the second asks for much larger memory requirements.
I saw in the code (drivers/pci/iov.c) that the order of the allocation
starts from the first BAR to the last.

The code:
for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
  res = iov->res + i;
  if (!res->flags)
      continue;
  rc = pci_assign_resource(dev, i + PCI_IOV_RESOURCES);

This process failed for the second BAR (The big one). (in the log: "not
enough MMIO resources for SR-IOV")

I think (IMHO) it because the allocation of the first BAR (the little)
one was from the allocated slot of the big one (the allocation from the
sriov_init function)
and when the kernel tries to allocate the slot for he second BAR (the
big one) in the place of the little one it failed.

when I changed the code to start the allocation from the last to the
first: for (i = PCI_SRIOV_NUM_BARS; i >= 0; i--) 
It works fine.

Is it a bug ? 

Thanks, Erez
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