Re: [Intel-gfx] [PATCH 10/12] drm/i915/guc: Support larger contexts on newer hardware

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: John Harrison <john.c.harrison@intel.com>,
	Intel-GFX@Lists.FreeDesktop.Org
Cc: DRI-Devel@Lists.FreeDesktop.Org
Subject: Re: [Intel-gfx] [PATCH 10/12] drm/i915/guc: Support larger contexts on newer hardware
Date: Tue, 19 Jul 2022 10:56:55 +0100	[thread overview]
Message-ID: <1f306c55-8443-72b3-a419-40f3cb85b76c@linux.intel.com> (raw)
In-Reply-To: <e7673834-a795-8364-96d9-7075bd407ee6@intel.com>

On 19/07/2022 01:13, John Harrison wrote:
> On 7/18/2022 05:35, Tvrtko Ursulin wrote:
>>
>> On 13/07/2022 00:31, John.C.Harrison@Intel.com wrote:
>>> From: Matthew Brost <matthew.brost@intel.com>
>>>
>>> The GuC needs a copy of a golden context for implementing watchdog
>>> resets (aka media resets). This context is larger on newer platforms.
>>> So adjust the size being allocated/copied accordingly.
>>
>> What were the consequences of this being too small? Media watchdog 
>> reset broken impacting userspace? Platforms? Do we have an IGT 
>> testcase? Do we need a Fixes: tag? Copy stable?
> Yes. Not sure if we have an IGT for the media watchdog. I recall writing 
> something a long time back but I don't think it ever got merged due to 
> push back that I don't recall right now. And no because it only affects 
> DG2 onwards which is still forceprobed.

Right, hm, I don't know if the MBD SKU promise for DG2 relies on force 
probe removal or not. My impression certainly was that a bunch of uapi 
we recently merged made people happy in that respect - that we satisfied 
the commit to deliver that support with 5.19. Maybe I am wrong, or 
perhaps to err on the side of safety you could add the right Fixes: tag 
regardless? Pick some patch which enables GuC for DG2 if there isn't 
anything better I guess. Or you could check with James.

Regards,

Tvrtko

> John.
> 
> 
>>
>> Regards,
>>
>> Tvrtko
>>
>>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>>> ---
>>>   drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c | 10 +++++++---
>>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c 
>>> b/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
>>> index ba7541f3ca610..74cbe8eaf5318 100644
>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
>>> @@ -464,7 +464,11 @@ static void fill_engine_enable_masks(struct 
>>> intel_gt *gt,
>>>   }
>>>     #define LR_HW_CONTEXT_SIZE (80 * sizeof(u32))
>>> -#define LRC_SKIP_SIZE (LRC_PPHWSP_SZ * PAGE_SIZE + LR_HW_CONTEXT_SIZE)
>>> +#define XEHP_LR_HW_CONTEXT_SIZE (96 * sizeof(u32))
>>> +#define LR_HW_CONTEXT_SZ(i915) (GRAPHICS_VER_FULL(i915) >= 
>>> IP_VER(12, 50) ? \
>>> +                    XEHP_LR_HW_CONTEXT_SIZE : \
>>> +                    LR_HW_CONTEXT_SIZE)
>>> +#define LRC_SKIP_SIZE(i915) (LRC_PPHWSP_SZ * PAGE_SIZE + 
>>> LR_HW_CONTEXT_SZ(i915))
>>>   static int guc_prep_golden_context(struct intel_guc *guc)
>>>   {
>>>       struct intel_gt *gt = guc_to_gt(guc);
>>> @@ -525,7 +529,7 @@ static int guc_prep_golden_context(struct 
>>> intel_guc *guc)
>>>            * on all engines).
>>>            */
>>>           ads_blob_write(guc, ads.eng_state_size[guc_class],
>>> -                   real_size - LRC_SKIP_SIZE);
>>> +                   real_size - LRC_SKIP_SIZE(gt->i915));
>>>           ads_blob_write(guc, ads.golden_context_lrca[guc_class],
>>>                      addr_ggtt);
>>>   @@ -599,7 +603,7 @@ static void guc_init_golden_context(struct 
>>> intel_guc *guc)
>>>           }
>>>             GEM_BUG_ON(ads_blob_read(guc, 
>>> ads.eng_state_size[guc_class]) !=
>>> -               real_size - LRC_SKIP_SIZE);
>>> +               real_size - LRC_SKIP_SIZE(gt->i915));
>>>           GEM_BUG_ON(ads_blob_read(guc, 
>>> ads.golden_context_lrca[guc_class]) != addr_ggtt);
>>>             addr_ggtt += alloc_size;
> 