linux-kernel - Re: Boot problem on PPC with 4.4-git

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Message-ID: <CAPcyv4jOkNmTj5OmevkaaJxJACcz-8t0wWRVKZp+ECR-Bm0SJA@mail.gmail.com>
Date:	Wed, 20 Jan 2016 12:33:17 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

On Wed, Jan 20, 2016 at 12:16 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> On Wed, Jan 20, 2016 at 12:08 PM, Dan Williams <dan.j.williams@...el.com> wrote:
>> On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
>> <Larry.Finger@...inger.net> wrote:
>>> My PowerBook G4 Aluminum with a 32-bit PPC processor fails to boot for the
>>> 4.4-git series. The problem was bisected to commit 21266be. It took a while
>>> to figure out why a commit that only rearranges the Kconfig files could
>>> cause the problem.
>>>
>>> The answer came when I read the commit message for 90a545e98126 and saw that
>>> "Recompiling with CONFIG_IO_STRICT_DEVMEM=n" might be necessary. After I
>>> made that change, the system boots.
>>>
>>> If it is the graphics hardware driver at fault, the VGA controller is listed
>>> as an ATI RV350 [Mobility Radeon 9600 M10] with PCI ID 1002:4350. It uses
>>> radeon as the driver.
>>>
>>> I'm not sure if this is a bug in the configuration, but I know that
>>> selecting the default answer to all the new configuration parameters leaves
>>> me with a machine that is unbootable.
>>
>> I agree that the default configuration should remain bootable.  I'll
>> send a change that does not force that default.
>>
>> Thanks for the report and sorry for the inconvenience.
>
> Are you sure that the bisect is pointing to "21266be9ed54 arch:
> consolidate CONFIG_STRICT_DEVM in lib/Kconfig.debug" and not
> "90a545e98126 restrict /dev/mem to idle io memory ranges"?  The
> default for CONFIG_STRICT_DEVM should be unchanged in 21266be9ed54,
> it's not until 90a545e98126 that I would expect a behavior change.

Sorry for the mail flurry... if you can verify that the following
change resolves this problem I'll send it up:

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f75a33f29f6e..7d0b49c536c5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1919,7 +1919,6 @@ config STRICT_DEVMEM
config IO_STRICT_DEVMEM
       bool "Filter I/O access to /dev/mem"
       depends on STRICT_DEVMEM
-       default STRICT_DEVMEM
       ---help---
         If this option is disabled, you allow userspace (root) access to all
         io-memory regardless of whether a driver is actively using that