linux-kernel - Re: [PATCH 0/2] PCI: PCI-E MPS bug fixes

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Date:	Tue, 13 Sep 2011 15:17:32 -0300
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Jon Mason <mason@...i.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH 0/2] PCI: PCI-E MPS bug fixes

On Tue, 2011-09-13 at 07:50 -0300, Benjamin Herrenschmidt wrote:
> > 
> > You should apply them. I would queue them, and but I don't have
> > another PCI tree anywhere for you to pull them. 
> > 
> > In fact, I'll be out for the next few weeks; I'll ask Bjorn to cover
> > for me. 
> 
> Note that I might be missing some patches, but what's currently in Linus
> tree is rather wrong.
> 
> The comment is right, but the implementation is bogus:

Oh and another one (again, I never saw the patches I'm responding to for
some odd reason, only email 0/2, so you might have already fixed that):

When using "safe" mode, I get a crash in pcie_find_smpss(). Patch below.

>From 1b542d690323fab332e61099193d598c5c515d13 Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Date: Tue, 13 Sep 2011 15:16:33 -0300
Subject: [PATCH] pci: Don't crash when reading mpss from root complex

In pcie_find_smpss(), we have the following statement:

 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
	    dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))

The problem is that at least on my machine, this gets called for the
root complex (virtual P2P bridge), and dev->bus->self is NULL since
the parent bus for this is not itself anchor to a PCI device.

This adds the necessary NULL check.

Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
---
 drivers/pci/probe.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8473727..09d1c0f 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1351,7 +1351,8 @@ static int pcie_find_smpss(struct pci_dev *dev, void *data)
 	 * will occur as normal.
 	 */
 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
-	    dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))
+	     (dev->bus->self &&
+	      dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT)))
 		*smpss = 0;
 
 	if (*smpss > dev->pcie_mpss)
-- 
1.7.4.1






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