[Intel-gfx] [PATCH v2 1/2] drm/i915: drop one bit on the hw_id when using guc

[Michel Thierry]

On 6/1/2018 8:10 AM, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2018-06-01 10:52:14)
>> We currently using GuC as a proxy to the hardware. When Guc is used in
>> such mode, it consumes the bit 20 of the hw_id to indicate that the
>> workload was submitted by proxy.
>>
>> So far we probably haven't seen the issue because we need to allocate
>> 1048576+ contexts to hit this issue. Still, we should avoid allocating
>> the hw_id on that bit and restriction to bits [0:19] (i.e 20bits
>> instead of 21).
>>
>> v2: Leave the max hw_id computation in i915_gem_context.c (Michel)
>>
>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
>> BSpec: 1237
>> ---
>>   drivers/gpu/drm/i915/i915_drv.h         |  1 +
>>   drivers/gpu/drm/i915/i915_gem_context.c | 14 +++++++++++---
>>   drivers/gpu/drm/i915/intel_lrc.c        |  2 +-
>>   3 files changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 38157df6ff5c..7088a1c3b6ad 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -1841,6 +1841,7 @@ struct drm_i915_private {
>>                   */
>>                  struct ida hw_ida;
>>   #define MAX_CONTEXT_HW_ID (1<<21) /* exclusive */
>> +#define MAX_GUC_CONTEXT_HW_ID (1<<20) /* exclusive */
>>   #define GEN11_MAX_CONTEXT_HW_ID (1<<11) /* exclusive */
>>          } contexts;
>>   
>> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
>> index 81f086397d10..fa732592e221 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_context.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
>> @@ -208,10 +208,18 @@ static int assign_hw_id(struct drm_i915_private *dev_priv, unsigned *out)
>>          int ret;
>>          unsigned int max;
>>   
>> -       if (INTEL_GEN(dev_priv) >= 11)
>> +       if (INTEL_GEN(dev_priv) >= 11) {
>>                  max = GEN11_MAX_CONTEXT_HW_ID;
>> -       else
>> -               max = MAX_CONTEXT_HW_ID;
>> +       } else {
>> +               /*
>> +                * When using GuC in proxy submission, GuC consumes the
>> +                * highest bit in the context id to indicate proxy submission.
>> +                */
>> +               max = USES_GUC_SUBMISSION(dev_priv) ?
>> +                       MAX_GUC_CONTEXT_HW_ID :
>> +                       MAX_CONTEXT_HW_ID;
> 
> I'm just going to say mixing if() and ternary ?: isn't great style.
> 
> Acked-by: Chris Wilson <chris at chris-wilson.co.uk>

My r-b from v1 still applies, but since I'm already writing this...

Reviewed-by: Michel Thierry <michel.thierry at intel.com>