[PATCH] drm/ttm: enable eviction for Per-VM-BO

[Thomas Hellstrom]

On 12/15/2017 10:13 AM, Christian König wrote:
> Hi Thomas,
>
> actually I was very happy to get rid of that stuff.

Yes, wrappers that don't do anything don't make much sense, but this is 
a different story.

>
> In the long run I indeed wanted to replace ctx->resv with the 
> ww_acquire_ctx to enable eviction of even more things, but that is a 
> different story.
>
> Recursive locking is usually something we should try to avoid.

Well this is more or less replicating what you are doing currently but 
instead of spreading the checks and locking state all over the code, 
both as local variables and parameters this is keeping it in a single 
place with correctness checks.

I agree recursive locking is generally frowned upon, but you're already 
doing it, not by using recursive locks, but by passing locking state 
around which IMO is worse.

Collecting the state in a the operation_ctx will make that usage-pattern 
more obvious but will help make the code cleaner and less error prone.

/Thomas



>
> Regards,
> Christian.
>
> Am 15.12.2017 um 08:01 schrieb Thomas Hellstrom:
>> Roger and Chrisitian,
>>
>> Correct me if I'm wrong, but It seems to me like a lot of the recent 
>> changes to ttm_bo.c are to allow recursive reservation object locking 
>> in the case of shared reservation objects, but only in certain 
>> functions and with special arguments so it doesn't look like 
>> recursive locking to the lockdep checker. Wouldn't it be a lot 
>> cleaner if we were to hide all this in a resurrected __ttm_bo_reserve 
>> something along the lines of
>>
>> int __ttm_bo_reserve(struct ttm_bo *bo, struct ttm_operation_ctx *ctx) {
>>     if (ctx && ctx->resv == bo->resv) {
>> #ifdef CONFIG_LOCKDEP
>>         WARN_ON(bo->reserved);
>> lockdep_assert_held(&ctx->resv);
>>         ctx->reserve_count++;
>> bo->reserved = true;
>> #endif
>>         return0;
>>      } else {
>>         int ret = reservation_object_lock(bo->resv, NULL) ? 0:-EBUSY;
>>
>>         if (ret)
>>             return ret;
>> #ifdef CONFIG_LOCKDEP
>>         WARN_ON(bo->reserved);
>>         bo->reserved = true;
>> #endif
>>         return 0;
>> }
>>
>> And similar for tryreserve and unreserve? Perhaps with a 
>> ww_acquire_ctx included somewhere as well...
>>
>> /Thomas
>>
>>
>>
>>
>> On 12/14/2017 09:10 AM, Roger He wrote:
>>> Change-Id: I0c6ece0decd18d30ccc94e5c7ca106d351941c62
>>> Signed-off-by: Roger He <Hongbo.He at amd.com>
>>> ---
>>>   drivers/gpu/drm/ttm/ttm_bo.c | 11 +++++------
>>>   1 file changed, 5 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
>>> b/drivers/gpu/drm/ttm/ttm_bo.c
>>> index 098b22e..ba5b486 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>>> @@ -707,7 +707,6 @@ bool ttm_bo_eviction_valuable(struct 
>>> ttm_buffer_object *bo,
>>>   EXPORT_SYMBOL(ttm_bo_eviction_valuable);
>>>     static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>>> -                   struct reservation_object *resv,
>>>                      uint32_t mem_type,
>>>                      const struct ttm_place *place,
>>>                      struct ttm_operation_ctx *ctx)
>>> @@ -722,8 +721,9 @@ static int ttm_mem_evict_first(struct 
>>> ttm_bo_device *bdev,
>>>       spin_lock(&glob->lru_lock);
>>>       for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>>>           list_for_each_entry(bo, &man->lru[i], lru) {
>>> -            if (bo->resv == resv) {
>>> -                if (list_empty(&bo->ddestroy))
>>> +            if (bo->resv == ctx->resv) {
>>> +                if (!ctx->allow_reserved_eviction &&
>>> +                    list_empty(&bo->ddestroy))
>>>                       continue;
>>>               } else {
>>>                   locked = reservation_object_trylock(bo->resv);
>>> @@ -835,7 +835,7 @@ static int ttm_bo_mem_force_space(struct 
>>> ttm_buffer_object *bo,
>>>               return ret;
>>>           if (mem->mm_node)
>>>               break;
>>> -        ret = ttm_mem_evict_first(bdev, bo->resv, mem_type, place, 
>>> ctx);
>>> +        ret = ttm_mem_evict_first(bdev, mem_type, place, ctx);
>>>           if (unlikely(ret != 0))
>>>               return ret;
>>>       } while (1);
>>> @@ -1332,8 +1332,7 @@ static int ttm_bo_force_list_clean(struct 
>>> ttm_bo_device *bdev,
>>>       for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>>>           while (!list_empty(&man->lru[i])) {
>>>               spin_unlock(&glob->lru_lock);
>>> -            ret = ttm_mem_evict_first(bdev, NULL, mem_type,
>>> -                          NULL, &ctx);
>>> +            ret = ttm_mem_evict_first(bdev, mem_type, NULL, &ctx);
>>>               if (ret)
>>>                   return ret;
>>>               spin_lock(&glob->lru_lock);
>>
>>