[Intel-xe] [PATCH] drm/xe: Extend drm_xe_vm_bind_op

[Mika Kuoppala]

Rodrigo Vivi <rodrigo.vivi at intel.com> writes:

> On Mon, Sep 04, 2023 at 05:46:44PM +0300, Mika Kuoppala wrote:
>> The bind api is extensible but for a single bind op, there
>> is not a mechanism to extend. Add extensions field to
>> struct drm_xe_vm_bind_op.
>
> But why would you want to extend the operation?
> Except for the destroy ones, every ioctl itself is extensible.
>
> So, DRM_IOCTL_XE_VM_BIND is extensible. Why would we need to get
> prepared to extend the operations themselves? And if we extend
> the operation, what to do with the extension at the ioctl level?
> which one has precedence? how to organize that?
>

The intent is to pass debugger metadata as part of particular
vm bind operation. For example on MAP, we could associate
ELF/ISA (relevant parts) as metadata for this bind range.

So in vector of binds, we want to tag specific one map (in between)
with debugger metadata.

With extending the XE_VM_BIND itself, this could be possible too
but would then need to deliver index into the vector instead
of carrying the metadata as part of per operation.
As atleast in this example, the extension is heavily tied
into particular OP (map).

I take that you mean precedence of VM_BIND vs bind op?
Excellent question and I dont know all the use cases the
vm_bind have to cater. So I can only refer to example above,
VM_BIND extensions would be only in scope to all operations
and vm_bind_op extensions would be tightly coupled to per
operation only.

Thanks for feedback!
-Mika

>> 
>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>> Cc: Matthew Brost <matthew.brost at intel.com>
>> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>> Cc: Francois Dugast <francois.dugast at intel.com>
>> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>> Cc: Dominik Grzegorzek <dominik.grzegorzek at intel.com>
>> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>> ---
>>  include/uapi/drm/xe_drm.h | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
>> index 86f16d50e9cc..5c6c86f5e5fc 100644
>> --- a/include/uapi/drm/xe_drm.h
>> +++ b/include/uapi/drm/xe_drm.h
>> @@ -552,6 +552,9 @@ struct drm_xe_vm_destroy {
>>  };
>>  
>>  struct drm_xe_vm_bind_op {
>> +	/** @extensions: Pointer to the first extension struct, if any */
>> +	__u64 extensions;
>> +
>>  	/**
>>  	 * @obj: GEM object to operate on, MBZ for MAP_USERPTR, MBZ for UNMAP
>>  	 */
>> -- 
>> 2.34.1
>>