[Intel-gfx] [PATCH 02/12] drm/i915/guc: Keep the ctx_pool_vaddr mapped, for easy access

[Oscar Mateo]

On 03/22/2017 02:45 AM, Chris Wilson wrote:
> On Tue, Mar 21, 2017 at 02:02:47AM -0700, Oscar Mateo wrote:
>> The GuC descriptor is big in size. If we use a local definition of
>> guc_desc we have a chance to overflow stack, so avoid it.
>>
>> Also, Chris abhors scatterlists :)
>>
>> v2: Rebased, helper function to retrieve the context descriptor,
>> s/ctx_pool_vma/ctx_pool/
>>
>> v3: Zero out guc_context_desc before initialization
>>
>> v4: Do not do arithmetic on void pointers
>>
>> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
>> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
>> Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>> Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_guc_submission.c | 93 +++++++++++++++---------------
>>   drivers/gpu/drm/i915/intel_guc_loader.c    |  2 +-
>>   drivers/gpu/drm/i915/intel_uc.h            |  3 +-
>>   3 files changed, 48 insertions(+), 50 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
>> index 21dadc1..5870cec 100644
>> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
>> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
>> @@ -133,6 +133,12 @@ static int __guc_deallocate_doorbell(struct intel_guc *guc, u32 ctx_index)
>>   	return intel_guc_send(guc, action, ARRAY_SIZE(action));
>>   }
>>   
>> +static struct guc_context_desc *__get_context_desc(struct i915_guc_client *client)
>> +{
>> +	return (struct guc_context_desc *)((char *)client->guc->ctx_pool_vaddr +
> We can use gccisms like using void * for arithmetic computations in the
> kernel, i.e.
> 	void *base = client->guc->ctx_pool_vaddr;
> 	return base + sizeof(struct guc_context_desc) * client->ctx_index;
> is just fine.
> -Chris

:_(
I got convinced by a previous review comment that arithmetic with void 
pointers was frowned upon.
Ok, thanks!