Boot problem on PPC with 4.4-git - Bisected to commit 21266be

Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Larry Finger]

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.

Larry

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Dan Williams]

On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
<Larry.Finger@lwfinger.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.

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Dan Williams]

On Wed, Jan 20, 2016 at 12:08 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
> <Larry.Finger@lwfinger.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.

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Dan Williams]

On Wed, Jan 20, 2016 at 12:16 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Wed, Jan 20, 2016 at 12:08 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>> On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
>> <Larry.Finger@lwfinger.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

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Larry Finger]

On 01/20/2016 02:33 PM, Dan Williams wrote:
> On Wed, Jan 20, 2016 at 12:16 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>> On Wed, Jan 20, 2016 at 12:08 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>>> On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
>>> <Larry.Finger@lwfinger.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

That isn't quite right. I added that patch, and restored the 4.4.0 
configuration. That one has "CONFIG_STRICT_DEVM=y". After I ran "make 
oldconfig", CONFIG_STRICT_DEVM was still set, which kills rebooting.

When I repeated the process, but removed the CONFIG_STRICT_DEVM line from 
.config before I ran "make oldconfig", then I got a bootable configuration. It 
seems that once STRICT_DEVM is yes, only a "make menuconfig", or equivalent, 
will let you turn it off.

Larry

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Dan Williams]

On Wed, Jan 20, 2016 at 1:36 PM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
> On 01/20/2016 02:33 PM, Dan Williams wrote:
> That isn't quite right. I added that patch, and restored the 4.4.0
> configuration. That one has "CONFIG_STRICT_DEVM=y". After I ran "make
> oldconfig", CONFIG_STRICT_DEVM was still set, which kills rebooting.
>
> When I repeated the process, but removed the CONFIG_STRICT_DEVM line from
> .config before I ran "make oldconfig", then I got a bootable configuration.
> It seems that once STRICT_DEVM is yes, only a "make menuconfig", or
> equivalent, will let you turn it off.

This matches my expectation.  The fix stops defaulting it on when
CONFIG_STRICT_DEVM is set, but if you already have it set this change
will have no effect.  In other words if you take a old config from
before CONFIG_IO_STRICT_DEVMEM was introduced it won't get turned
on...

Re: Boot problem on PPC with 4.4-git - Bisected to commit 21266be

[Larry Finger]

On 01/20/2016 02:16 PM, Dan Williams wrote:
> On Wed, Jan 20, 2016 at 12:08 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>> On Wed, Jan 20, 2016 at 12:01 PM, Larry Finger
>> <Larry.Finger@lwfinger.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.

Yes. Commit 21266be9ed54 was the reported bad commit; however, the previous test 
kernel was 90a545e98126. In fact, I was struck that the final bisection build 
did not change any object files, thus you are right that 90a545e98126 is likely 
the bad commit.

Larry