Re: [PATCH 0/5]PCI: x86 MMCONFIG

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Greg KH]

On Wed, Dec 19, 2007 at 05:17:46PM -0500, tcamuso@redhat.com wrote:
> OVERVIEW
> =======
> 
> The patches should be applied in sequence to obviate any
> possible build problems.
> 
> The patch-set was built against 2.6.24-rc5
> 
> Description
> ===========
> 
> There exist devices that do not respond correctly to PCI
> MMCONFIG accesses in x86 platforms.

What devices are these?  Do you have reports of them somewhere?

> This patch-set detects the problem by comparing an MMCONFIG
> read to a Legacy PCI config read of the vendor/device dword
> of every device discovered during the PCI probing sequence.
> 
> A miscompare means that a device does not correctly respond
> to MMCONFIG accesses. When the patch code detects this condition,
> the bus that serves this device, and all subordinate buses, will
> be programmed to use Legacy PCI Config accesses.
> 
> This patch-set DOES NOT detect devices that generate machine
> checks against MMCONFIG accesses. For such systems,
> "pci=nommconf" is required in the boot command.

That sounds like this patchset can cause bad side affects on hardware
that currently works just fine.  That is not a good thing to be adding
to the kernel, right?

thanks,

greg k-h

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Robert Hancock]

Greg KH wrote:
> On Wed, Dec 19, 2007 at 05:17:46PM -0500, tcamuso@redhat.com wrote:
>> OVERVIEW
>> =======
>>
>> The patches should be applied in sequence to obviate any
>> possible build problems.
>>
>> The patch-set was built against 2.6.24-rc5
>>
>> Description
>> ===========
>>
>> There exist devices that do not respond correctly to PCI
>> MMCONFIG accesses in x86 platforms.
> 
> What devices are these?  Do you have reports of them somewhere?
> 
>> This patch-set detects the problem by comparing an MMCONFIG
>> read to a Legacy PCI config read of the vendor/device dword
>> of every device discovered during the PCI probing sequence.
>>
>> A miscompare means that a device does not correctly respond
>> to MMCONFIG accesses. When the patch code detects this condition,
>> the bus that serves this device, and all subordinate buses, will
>> be programmed to use Legacy PCI Config accesses.
>>
>> This patch-set DOES NOT detect devices that generate machine
>> checks against MMCONFIG accesses. For such systems,
>> "pci=nommconf" is required in the boot command.
> 
> That sounds like this patchset can cause bad side affects on hardware
> that currently works just fine.  That is not a good thing to be adding
> to the kernel, right?

I think we need more details on why this patch is needed. Also, we 
already have something like this in arch/x86/pci/mmconfig-shared.c, in 
the unreachable_devices function. This attempts to detect devices where 
MMCONFIG cannot access the configuration space (one of these would be at 
least one device in the AMD K8 built-in northbridge). If this is not 
sufficient, I would suggest expanding that mechanism instead of adding 
all this new code.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Tony Camuso]

Greg,

Have you given this patch-set any more consideration?

I've submitted the changes you requested. 

Regards,
Tony

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Greg KH]

On Mon, Jan 07, 2008 at 10:20:23PM -0500, Tony Camuso wrote:
> Greg,
> 
> Have you given this patch-set any more consideration?

Which patch-set, there have been a number of them :)

> I've submitted the changes you requested. 

Care to respin them all so I'm not confused?

thanks,

greg k-h

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Tony Camuso]

I'll respin the whole kit with [PATCH ?/5][V2]PCI: x86 MMCONFIG *
in the subject line, where the ? is replaced by the number of the
patch within the set and the * is replaced by a brief description,
if that's acceptable.

I can have it ready in a few hours. 

On Mon, 2008-01-07 at 20:56 -0800, Greg KH wrote:
> On Mon, Jan 07, 2008 at 10:20:23PM -0500, Tony Camuso wrote:
> > Greg,
> > 
> > Have you given this patch-set any more consideration?
> 
> Which patch-set, there have been a number of them :)
> 
> > I've submitted the changes you requested. 
> 
> Care to respin them all so I'm not confused?
> 
> thanks,
> 
> greg k-h

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Greg KH]

On Tue, Jan 08, 2008 at 08:14:22AM -0500, Tony Camuso wrote:
> I'll respin the whole kit with [PATCH ?/5][V2]PCI: x86 MMCONFIG *
> in the subject line, where the ? is replaced by the number of the
> patch within the set and the * is replaced by a brief description,
> if that's acceptable.

That sounds great.

> I can have it ready in a few hours. 

I'll be on a plane for a few hours, so don't feel the need to rush :)

thanks,

greg k-h

Re: [PATCH 0/5]PCI: x86 MMCONFIG

[Tony Camuso]

Thanks, Greg.

Have a safe flight!

On Tue, 2008-01-08 at 05:36 -0800, Greg KH wrote:
> On Tue, Jan 08, 2008 at 08:14:22AM -0500, Tony Camuso wrote:
> > I'll respin the whole kit with [PATCH ?/5][V2]PCI: x86 MMCONFIG *
> > in the subject line, where the ? is replaced by the number of the
> > patch within the set and the * is replaced by a brief description,
> > if that's acceptable.
> 
> That sounds great.
> 
> > I can have it ready in a few hours. 
> 
> I'll be on a plane for a few hours, so don't feel the need to rush :)
> 
> thanks,
> 
> greg k-h