Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Dan Williams]

On Thu, Sep 28, 2017 at 2:09 AM, Greg Kroah-Hartman
 wrote:
> On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
>> This patch introduces a new kernel command line parameter to mask pci
>> device ids from pci driver id tables. This prevents masked devices from
>> automatically binding to both built-in and module drivers.
>>
>> Devices can be later attached through the driver's sysfs new_id
>> inteface.
>>
>> The use cases for this are primarily for debugging, eg, being able to
>> prevent attachment before probes are set up. It can also be used to mask
>> off faulty built-in hardware or faulty simulated hardware.
>>
>> Another use case is to prevent attachment of devices which will be
>> passed to VMs, shortcutting the detachment effort.
>
> Is the "shortcut" really that big of a deal?  unbind actually causes
> problems?  Is this an attempt to deal with devices being handled by more
> than one driver and then you want to manually bind it later on?
>
>> The format is similar to the sysfs new_id format. Device ids are
>> specified with:
>>
>> :[:SVVV:SDDD][:][:]
>>
>> Where:
>>  = Vendor ID
>>  = Device ID
>> SVVV = Subvendor ID
>> SDDD = Subdevice ID
>>  = Class
>>  = Class Mask
>>
>> IDs can be chained with commas.
>>
>> Examples:
>>   .delete_id=1234:5678
>>   .delete_id=:
>>   .delete_id=::::010802
>>   .delete_id=1234:5678,abcd:ef01,2345:
>
> What about drivers that handle more than one bus type (i.e. USB and
> PCI?)  This format is specific to PCI, yet you are defining it as a
> "global" for all drivers :(

I assume other buses could define their own "delete_id" format and
it's up to those bus_type implementations to check for "delete_id"
statements for the drivers attached to it. Somewhat similar to what we
have for "new_id" where it appears to be global sysfs attribute, but
implemented per-bus.

> This feels hacky, what is the real reason for this?  It feels like we
> have so many different ways to blacklist and unbind and bind devices to
> drivers already, why add yet-another way?

Unbind after the fact may be too late, and builtin-drivers eliminate
modprobe blacklisting. I've missed having this functionality in the
past for platform bring up.

Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Dan Williams]

On Thu, Sep 28, 2017 at 2:09 AM, Greg Kroah-Hartman
 wrote:
> On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
>> This patch introduces a new kernel command line parameter to mask pci
>> device ids from pci driver id tables. This prevents masked devices from
>> automatically binding to both built-in and module drivers.
>>
>> Devices can be later attached through the driver's sysfs new_id
>> inteface.
>>
>> The use cases for this are primarily for debugging, eg, being able to
>> prevent attachment before probes are set up. It can also be used to mask
>> off faulty built-in hardware or faulty simulated hardware.
>>
>> Another use case is to prevent attachment of devices which will be
>> passed to VMs, shortcutting the detachment effort.
>
> Is the "shortcut" really that big of a deal?  unbind actually causes
> problems?  Is this an attempt to deal with devices being handled by more
> than one driver and then you want to manually bind it later on?
>
>> The format is similar to the sysfs new_id format. Device ids are
>> specified with:
>>
>> :[:SVVV:SDDD][:][:]
>>
>> Where:
>>  = Vendor ID
>>  = Device ID
>> SVVV = Subvendor ID
>> SDDD = Subdevice ID
>>  = Class
>>  = Class Mask
>>
>> IDs can be chained with commas.
>>
>> Examples:
>>   .delete_id=1234:5678
>>   .delete_id=:
>>   .delete_id=::::010802
>>   .delete_id=1234:5678,abcd:ef01,2345:
>
> What about drivers that handle more than one bus type (i.e. USB and
> PCI?)  This format is specific to PCI, yet you are defining it as a
> "global" for all drivers :(

I assume other buses could define their own "delete_id" format and
it's up to those bus_type implementations to check for "delete_id"
statements for the drivers attached to it. Somewhat similar to what we
have for "new_id" where it appears to be global sysfs attribute, but
implemented per-bus.

> This feels hacky, what is the real reason for this?  It feels like we
> have so many different ways to blacklist and unbind and bind devices to
> drivers already, why add yet-another way?

Unbind after the fact may be too late, and builtin-drivers eliminate
modprobe blacklisting. I've missed having this functionality in the
past for platform bring up.

Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Jon Derrick]

Hi Greg,

On 09/28/2017 03:09 AM, Greg Kroah-Hartman wrote:
> On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
>> This patch introduces a new kernel command line parameter to mask pci
>> device ids from pci driver id tables. This prevents masked devices from
>> automatically binding to both built-in and module drivers.
>>
>> Devices can be later attached through the driver's sysfs new_id
>> inteface.
>>
>> The use cases for this are primarily for debugging, eg, being able to
>> prevent attachment before probes are set up. It can also be used to mask
>> off faulty built-in hardware or faulty simulated hardware.
>>
>> Another use case is to prevent attachment of devices which will be
>> passed to VMs, shortcutting the detachment effort.
> 
> Is the "shortcut" really that big of a deal?  unbind actually causes
> problems?  Is this an attempt to deal with devices being handled by more
> than one driver and then you want to manually bind it later on?
> 
>> The format is similar to the sysfs new_id format. Device ids are
>> specified with:
>>
>> :[:SVVV:SDDD][:][:]
>>
>> Where:
>>  = Vendor ID
>>  = Device ID
>> SVVV = Subvendor ID
>> SDDD = Subdevice ID
>>  = Class
>>  = Class Mask
>>
>> IDs can be chained with commas.
>>
>> Examples:
>>  .delete_id=1234:5678
>>  .delete_id=:
>>  .delete_id=::::010802
>>  .delete_id=1234:5678,abcd:ef01,2345:
> 
> What about drivers that handle more than one bus type (i.e. USB and
> PCI?)  This format is specific to PCI, yet you are defining it as a
> "global" for all drivers :(
> 
I was hoping to extend it to other bus types as well, but just wanted
some early feedback on the idea. Pci was the easier implementation for
me. Could prepending pci:, usb:, etc on the format be an option?

> This feels hacky, what is the real reason for this?  It feels like we
> have so many different ways to blacklist and unbind and bind devices to
> drivers already, why add yet-another way?
> 
I ran into an issue a while back where I needed to disable a device from
a built-in driver to perform a regression test. I worked around that
issue by doing an initcall_blacklist on the pci-driver declaration, but
that also preventing later binding because the driver was never registered.

I've also had issues with remote systems where pluggable devices were
broken or otherwise non-responsive, and it would have been nice to have
been able to keep them from binding on module loading as a temporary
workaround until someone could have removed those devices (though
impossible on built-in hardware).

I'm not sure about hacky; I think the implementation in this patch (1/3)
is pretty clean :). I'm not familiar with all the different ways of
blacklisting. Is there another way to work around the issues I listed above?

I understand the concern about having it exist in the format .
and only supporting one or a few bus types. I have another set that
extends the pci= parameter instead.

> thanks,
> 
> greg k-h
> 

Best,
Jon

Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Jon Derrick]

Hi Greg,

On 09/28/2017 03:09 AM, Greg Kroah-Hartman wrote:
> On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
>> This patch introduces a new kernel command line parameter to mask pci
>> device ids from pci driver id tables. This prevents masked devices from
>> automatically binding to both built-in and module drivers.
>>
>> Devices can be later attached through the driver's sysfs new_id
>> inteface.
>>
>> The use cases for this are primarily for debugging, eg, being able to
>> prevent attachment before probes are set up. It can also be used to mask
>> off faulty built-in hardware or faulty simulated hardware.
>>
>> Another use case is to prevent attachment of devices which will be
>> passed to VMs, shortcutting the detachment effort.
> 
> Is the "shortcut" really that big of a deal?  unbind actually causes
> problems?  Is this an attempt to deal with devices being handled by more
> than one driver and then you want to manually bind it later on?
> 
>> The format is similar to the sysfs new_id format. Device ids are
>> specified with:
>>
>> :[:SVVV:SDDD][:][:]
>>
>> Where:
>>  = Vendor ID
>>  = Device ID
>> SVVV = Subvendor ID
>> SDDD = Subdevice ID
>>  = Class
>>  = Class Mask
>>
>> IDs can be chained with commas.
>>
>> Examples:
>>  .delete_id=1234:5678
>>  .delete_id=:
>>  .delete_id=::::010802
>>  .delete_id=1234:5678,abcd:ef01,2345:
> 
> What about drivers that handle more than one bus type (i.e. USB and
> PCI?)  This format is specific to PCI, yet you are defining it as a
> "global" for all drivers :(
> 
I was hoping to extend it to other bus types as well, but just wanted
some early feedback on the idea. Pci was the easier implementation for
me. Could prepending pci:, usb:, etc on the format be an option?

> This feels hacky, what is the real reason for this?  It feels like we
> have so many different ways to blacklist and unbind and bind devices to
> drivers already, why add yet-another way?
> 
I ran into an issue a while back where I needed to disable a device from
a built-in driver to perform a regression test. I worked around that
issue by doing an initcall_blacklist on the pci-driver declaration, but
that also preventing later binding because the driver was never registered.

I've also had issues with remote systems where pluggable devices were
broken or otherwise non-responsive, and it would have been nice to have
been able to keep them from binding on module loading as a temporary
workaround until someone could have removed those devices (though
impossible on built-in hardware).

I'm not sure about hacky; I think the implementation in this patch (1/3)
is pretty clean :). I'm not familiar with all the different ways of
blacklisting. Is there another way to work around the issues I listed above?

I understand the concern about having it exist in the format .
and only supporting one or a few bus types. I have another set that
extends the pci= parameter instead.

> thanks,
> 
> greg k-h
> 

Best,
Jon

Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Greg Kroah-Hartman]

On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
> This patch introduces a new kernel command line parameter to mask pci
> device ids from pci driver id tables. This prevents masked devices from
> automatically binding to both built-in and module drivers.
> 
> Devices can be later attached through the driver's sysfs new_id
> inteface.
> 
> The use cases for this are primarily for debugging, eg, being able to
> prevent attachment before probes are set up. It can also be used to mask
> off faulty built-in hardware or faulty simulated hardware.
> 
> Another use case is to prevent attachment of devices which will be
> passed to VMs, shortcutting the detachment effort.

Is the "shortcut" really that big of a deal?  unbind actually causes
problems?  Is this an attempt to deal with devices being handled by more
than one driver and then you want to manually bind it later on?

> The format is similar to the sysfs new_id format. Device ids are
> specified with:
> 
> :[:SVVV:SDDD][:][:]
> 
> Where:
>  = Vendor ID
>  = Device ID
> SVVV = Subvendor ID
> SDDD = Subdevice ID
>  = Class
>  = Class Mask
> 
> IDs can be chained with commas.
> 
> Examples:
>   .delete_id=1234:5678
>   .delete_id=:
>   .delete_id=::::010802
>   .delete_id=1234:5678,abcd:ef01,2345:

What about drivers that handle more than one bus type (i.e. USB and
PCI?)  This format is specific to PCI, yet you are defining it as a
"global" for all drivers :(

This feels hacky, what is the real reason for this?  It feels like we
have so many different ways to blacklist and unbind and bind devices to
drivers already, why add yet-another way?

thanks,

greg k-h

Re: [RFC 1/3] PCI: pci-driver: Introduce pci device delete list

[Greg Kroah-Hartman]

On Wed, Sep 27, 2017 at 04:40:20PM -0400, Jon Derrick wrote:
> This patch introduces a new kernel command line parameter to mask pci
> device ids from pci driver id tables. This prevents masked devices from
> automatically binding to both built-in and module drivers.
> 
> Devices can be later attached through the driver's sysfs new_id
> inteface.
> 
> The use cases for this are primarily for debugging, eg, being able to
> prevent attachment before probes are set up. It can also be used to mask
> off faulty built-in hardware or faulty simulated hardware.
> 
> Another use case is to prevent attachment of devices which will be
> passed to VMs, shortcutting the detachment effort.

Is the "shortcut" really that big of a deal?  unbind actually causes
problems?  Is this an attempt to deal with devices being handled by more
than one driver and then you want to manually bind it later on?

> The format is similar to the sysfs new_id format. Device ids are
> specified with:
> 
> :[:SVVV:SDDD][:][:]
> 
> Where:
>  = Vendor ID
>  = Device ID
> SVVV = Subvendor ID
> SDDD = Subdevice ID
>  = Class
>  = Class Mask
> 
> IDs can be chained with commas.
> 
> Examples:
>   .delete_id=1234:5678
>   .delete_id=:
>   .delete_id=::::010802
>   .delete_id=1234:5678,abcd:ef01,2345:

What about drivers that handle more than one bus type (i.e. USB and
PCI?)  This format is specific to PCI, yet you are defining it as a
"global" for all drivers :(

This feels hacky, what is the real reason for this?  It feels like we
have so many different ways to blacklist and unbind and bind devices to
drivers already, why add yet-another way?

thanks,

greg k-h