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

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Message-ID: <CAMaF-rPhfVmuMthdO_iHEMmSbi9cujX7LrK+DTGHZ=FxGpdokg@mail.gmail.com>
Date:	Tue, 13 Sep 2011 16:05:54 -0500
From:	Jon Mason <mason@...i.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
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, Sep 13, 2011 at 1:17 PM, Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
> 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):

DNS issue with kernel.org when the patches went out caused it to not
get out to any of the mailing lists.

In Linux' github tree
Patch 1/2 is commit 5307f6d5fb12fd01f9f321bc4a8fd77e74858647
Patch 2/2 is commit ed2888e906b56769b4ffabb9c577190438aa68b8

> 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>

Good catch.

Acked-by: Jon Mason <mason@...i.com>

> ---
>  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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