Re: [PATCH v5 4/4] drm/i915/bdw: Pin the ringbuffer backing object to GGTT on-demand

[Deepak S <deepak.s@intel.com>]

On Tuesday 18 November 2014 12:07 PM, Deepak S wrote:
>
> On Thursday 13 November 2014 03:58 PM, Thomas Daniel wrote:
>> Same as with the context, pinning to GGTT regardless is harmful (it
>> badly fragments the GGTT and can even exhaust it).
>>
>> Unfortunately, this case is also more complex than the previous one
>> because we need to map and access the ringbuffer in several places
>> along the execbuffer path (and we cannot make do by leaving the
>> default ringbuffer pinned, as before). Also, the context object
>> itself contains a pointer to the ringbuffer address that we have to
>> keep updated if we are going to allow the ringbuffer to move around.
>>
>> v2: Same as with the context pinning, we cannot really do it during
>> an interrupt. Also, pin the default ringbuffers objects regardless
>> (makes error capture a lot easier).
>>
>> v3: Rebased. Take a pin reference of the ringbuffer for each item
>> in the execlist request queue because the hardware may still be using
>> the ringbuffer after the MI_USER_INTERRUPT to notify the seqno update
>> is executed.  The ringbuffer must remain pinned until the context save
>> is complete.  No longer pin and unpin ringbuffer in
>> populate_lr_context() - this transient address is meaningless and the
>> pinning can cause a sleep while atomic.
>>
>> v4: Moved ringbuffer pin and unpin into the lr_context_pin functions.
>> Downgraded pinning check BUG_ONs to WARN_ONs.
>>
>> v5: Reinstated WARN_ONs for unexpected execlist states.  Removed unused
>> variable.
>>
>> Issue: VIZ-4277
>> Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
>> Signed-off-by: Thomas Daniel <thomas.daniel@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_lrc.c        |  102 
>> +++++++++++++++++++++++--------
>>   drivers/gpu/drm/i915/intel_ringbuffer.c |   85 
>> +++++++++++++++-----------
>>   drivers/gpu/drm/i915/intel_ringbuffer.h |    3 +
>>   3 files changed, 128 insertions(+), 62 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c 
>> b/drivers/gpu/drm/i915/intel_lrc.c
>> index f7fa0f7..ca20f91 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -202,6 +202,9 @@ enum {
>>   };
>>   #define GEN8_CTX_ID_SHIFT 32
>>   +static int intel_lr_context_pin(struct intel_engine_cs *ring,
>> +        struct intel_context *ctx);
>> +
>>   /**
>>    * intel_sanitize_enable_execlists() - sanitize i915.enable_execlists
>>    * @dev: DRM device.
>> @@ -339,7 +342,9 @@ static void execlists_elsp_write(struct 
>> intel_engine_cs *ring,
>>       spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
>>   }
>>   -static int execlists_ctx_write_tail(struct drm_i915_gem_object 
>> *ctx_obj, u32 tail)
>> +static int execlists_update_context(struct drm_i915_gem_object 
>> *ctx_obj,
>> +                    struct drm_i915_gem_object *ring_obj,
>> +                    u32 tail)
>>   {
>>       struct page *page;
>>       uint32_t *reg_state;
>> @@ -348,6 +353,7 @@ static int execlists_ctx_write_tail(struct 
>> drm_i915_gem_object *ctx_obj, u32 tai
>>       reg_state = kmap_atomic(page);
>>         reg_state[CTX_RING_TAIL+1] = tail;
>> +    reg_state[CTX_RING_BUFFER_START+1] = 
>> i915_gem_obj_ggtt_offset(ring_obj);
>>         kunmap_atomic(reg_state);
>>   @@ -358,21 +364,25 @@ static int execlists_submit_context(struct 
>> intel_engine_cs *ring,
>>                       struct intel_context *to0, u32 tail0,
>>                       struct intel_context *to1, u32 tail1)
>>   {
>> -    struct drm_i915_gem_object *ctx_obj0;
>> +    struct drm_i915_gem_object *ctx_obj0 = to0->engine[ring->id].state;
>> +    struct intel_ringbuffer *ringbuf0 = to0->engine[ring->id].ringbuf;
>>       struct drm_i915_gem_object *ctx_obj1 = NULL;
>> +    struct intel_ringbuffer *ringbuf1 = NULL;
>>   -    ctx_obj0 = to0->engine[ring->id].state;
>>       BUG_ON(!ctx_obj0);
>>       WARN_ON(!i915_gem_obj_is_pinned(ctx_obj0));
>> +    WARN_ON(!i915_gem_obj_is_pinned(ringbuf0->obj));
>>   -    execlists_ctx_write_tail(ctx_obj0, tail0);
>> +    execlists_update_context(ctx_obj0, ringbuf0->obj, tail0);
>>         if (to1) {
>> +        ringbuf1 = to1->engine[ring->id].ringbuf;
>>           ctx_obj1 = to1->engine[ring->id].state;
>>           BUG_ON(!ctx_obj1);
>>           WARN_ON(!i915_gem_obj_is_pinned(ctx_obj1));
>> +        WARN_ON(!i915_gem_obj_is_pinned(ringbuf1->obj));
>>   -        execlists_ctx_write_tail(ctx_obj1, tail1);
>> +        execlists_update_context(ctx_obj1, ringbuf1->obj, tail1);
>>       }
>>         execlists_elsp_write(ring, ctx_obj0, ctx_obj1);
>> @@ -524,6 +534,10 @@ static int execlists_context_queue(struct 
>> intel_engine_cs *ring,
>>           return -ENOMEM;
>>       req->ctx = to;
>>       i915_gem_context_reference(req->ctx);
>> +
>> +    if (to != ring->default_context)
>> +        intel_lr_context_pin(ring, to);
>> +
>>       req->ring = ring;
>>       req->tail = tail;
>>   @@ -544,7 +558,7 @@ static int execlists_context_queue(struct 
>> intel_engine_cs *ring,
>>             if (to == tail_req->ctx) {
>>               WARN(tail_req->elsp_submitted != 0,
>> -                 "More than 2 already-submitted reqs queued\n");
>> +                "More than 2 already-submitted reqs queued\n");
>>               list_del(&tail_req->execlist_link);
>>               list_add_tail(&tail_req->execlist_link,
>>                   &ring->execlist_retired_req_list);
>> @@ -732,6 +746,12 @@ void intel_execlists_retire_requests(struct 
>> intel_engine_cs *ring)
>>       spin_unlock_irqrestore(&ring->execlist_lock, flags);
>>         list_for_each_entry_safe(req, tmp, &retired_list, 
>> execlist_link) {
>> +        struct intel_context *ctx = req->ctx;
>> +        struct drm_i915_gem_object *ctx_obj =
>> +                ctx->engine[ring->id].state;
>> +
>> +        if (ctx_obj && (ctx != ring->default_context))
>> +            intel_lr_context_unpin(ring, ctx);
>>           intel_runtime_pm_put(dev_priv);
>>           i915_gem_context_unreference(req->ctx);
>>           list_del(&req->execlist_link);
>> @@ -803,6 +823,7 @@ static int intel_lr_context_pin(struct 
>> intel_engine_cs *ring,
>>           struct intel_context *ctx)
>>   {
>>       struct drm_i915_gem_object *ctx_obj = ctx->engine[ring->id].state;
>> +    struct intel_ringbuffer *ringbuf = ctx->engine[ring->id].ringbuf;
>>       int ret = 0;
>> WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
>> @@ -810,21 +831,35 @@ static int intel_lr_context_pin(struct 
>> intel_engine_cs *ring,
>>           ret = i915_gem_obj_ggtt_pin(ctx_obj,
>>                   GEN8_LR_CONTEXT_ALIGN, 0);
>>           if (ret)
>> -            ctx->engine[ring->id].unpin_count = 0;
>> +            goto reset_unpin_count;
>> +
>> +        ret = intel_pin_and_map_ringbuffer_obj(ring->dev, ringbuf);
>> +        if (ret)
>> +            goto unpin_ctx_obj;
>>       }
>>         return ret;
>> +
>> +unpin_ctx_obj:
>> +    i915_gem_object_ggtt_unpin(ctx_obj);
>> +reset_unpin_count:
>> +    ctx->engine[ring->id].unpin_count = 0;
>> +
>> +    return ret;
>>   }
>>     void intel_lr_context_unpin(struct intel_engine_cs *ring,
>>           struct intel_context *ctx)
>>   {
>>       struct drm_i915_gem_object *ctx_obj = ctx->engine[ring->id].state;
>> +    struct intel_ringbuffer *ringbuf = ctx->engine[ring->id].ringbuf;
>>         if (ctx_obj) {
>> WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
>
> With pin specific mutex from previous patch set removed

Oops This comment was for previous patch in the series :( Since i reviewed the patch offline, comments got mixed :)
Anyways you patch looks fine,  Reviewed-by: Deepak S<deepak.s@linux.intel.com>

> Reviewed-by: Deepak S<deepak.s@linux.intel.com>
>
>> -        if (--ctx->engine[ring->id].unpin_count == 0)
>> +        if (--ctx->engine[ring->id].unpin_count == 0) {
>> +            intel_unpin_ringbuffer_obj(ringbuf);
>>               i915_gem_object_ggtt_unpin(ctx_obj);
>> +        }
>>       }
>>   }
>>   @@ -1541,7 +1576,6 @@ populate_lr_context(struct intel_context 
>> *ctx, struct drm_i915_gem_object *ctx_o
>>   {
>>       struct drm_device *dev = ring->dev;
>>       struct drm_i915_private *dev_priv = dev->dev_private;
>> -    struct drm_i915_gem_object *ring_obj = ringbuf->obj;
>>       struct i915_hw_ppgtt *ppgtt = ctx->ppgtt;
>>       struct page *page;
>>       uint32_t *reg_state;
>> @@ -1587,7 +1621,9 @@ populate_lr_context(struct intel_context *ctx, 
>> struct drm_i915_gem_object *ctx_o
>>       reg_state[CTX_RING_TAIL] = RING_TAIL(ring->mmio_base);
>>       reg_state[CTX_RING_TAIL+1] = 0;
>>       reg_state[CTX_RING_BUFFER_START] = RING_START(ring->mmio_base);
>> -    reg_state[CTX_RING_BUFFER_START+1] = 
>> i915_gem_obj_ggtt_offset(ring_obj);
>> +    /* Ring buffer start address is not known until the buffer is 
>> pinned.
>> +     * It is written to the context image in execlists_update_context()
>> +     */
>>       reg_state[CTX_RING_BUFFER_CONTROL] = RING_CTL(ring->mmio_base);
>>       reg_state[CTX_RING_BUFFER_CONTROL+1] =
>>               ((ringbuf->size - PAGE_SIZE) & RING_NR_PAGES) | 
>> RING_VALID;
>> @@ -1669,10 +1705,12 @@ void intel_lr_context_free(struct 
>> intel_context *ctx)
>>                       ctx->engine[i].ringbuf;
>>               struct intel_engine_cs *ring = ringbuf->ring;
>>   +            if (ctx == ring->default_context) {
>> +                intel_unpin_ringbuffer_obj(ringbuf);
>> +                i915_gem_object_ggtt_unpin(ctx_obj);
>> +            }
>>               intel_destroy_ringbuffer_obj(ringbuf);
>>               kfree(ringbuf);
>> -            if (ctx == ring->default_context)
>> -                i915_gem_object_ggtt_unpin(ctx_obj);
>>               drm_gem_object_unreference(&ctx_obj->base);
>>           }
>>       }
>> @@ -1770,11 +1808,8 @@ int intel_lr_context_deferred_create(struct 
>> intel_context *ctx,
>>       if (!ringbuf) {
>>           DRM_DEBUG_DRIVER("Failed to allocate ringbuffer %s\n",
>>                   ring->name);
>> -        if (is_global_default_ctx)
>> -            i915_gem_object_ggtt_unpin(ctx_obj);
>> -        drm_gem_object_unreference(&ctx_obj->base);
>>           ret = -ENOMEM;
>> -        return ret;
>> +        goto error_unpin_ctx;
>>       }
>>         ringbuf->ring = ring;
>> @@ -1787,22 +1822,30 @@ int intel_lr_context_deferred_create(struct 
>> intel_context *ctx,
>>       ringbuf->space = ringbuf->size;
>>       ringbuf->last_retired_head = -1;
>>   -    /* TODO: For now we put this in the mappable region so that we 
>> can reuse
>> -     * the existing ringbuffer code which ioremaps it. When we start
>> -     * creating many contexts, this will no longer work and we must 
>> switch
>> -     * to a kmapish interface.
>> -     */
>> -    ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
>> -    if (ret) {
>> -        DRM_DEBUG_DRIVER("Failed to allocate ringbuffer obj %s: %d\n",
>> +    if (ringbuf->obj == NULL) {
>> +        ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
>> +        if (ret) {
>> +            DRM_DEBUG_DRIVER(
>> +                "Failed to allocate ringbuffer obj %s: %d\n",
>>                   ring->name, ret);
>> -        goto error;
>> +            goto error_free_rbuf;
>> +        }
>> +
>> +        if (is_global_default_ctx) {
>> +            ret = intel_pin_and_map_ringbuffer_obj(dev, ringbuf);
>> +            if (ret) {
>> +                DRM_ERROR(
>> +                    "Failed to pin and map ringbuffer %s: %d\n",
>> +                    ring->name, ret);
>> +                goto error_destroy_rbuf;
>> +            }
>> +        }
>> +
>>       }
>>         ret = populate_lr_context(ctx, ctx_obj, ring, ringbuf);
>>       if (ret) {
>>           DRM_DEBUG_DRIVER("Failed to populate LRC: %d\n", ret);
>> -        intel_destroy_ringbuffer_obj(ringbuf);
>>           goto error;
>>       }
>>   @@ -1823,7 +1866,6 @@ int intel_lr_context_deferred_create(struct 
>> intel_context *ctx,
>>               DRM_ERROR("Init render state failed: %d\n", ret);
>>               ctx->engine[ring->id].ringbuf = NULL;
>>               ctx->engine[ring->id].state = NULL;
>> -            intel_destroy_ringbuffer_obj(ringbuf);
>>               goto error;
>>           }
>>           ctx->rcs_initialized = true;
>> @@ -1832,7 +1874,13 @@ int intel_lr_context_deferred_create(struct 
>> intel_context *ctx,
>>       return 0;
>>     error:
>> +    if (is_global_default_ctx)
>> +        intel_unpin_ringbuffer_obj(ringbuf);
>> +error_destroy_rbuf:
>> +    intel_destroy_ringbuffer_obj(ringbuf);
>> +error_free_rbuf:
>>       kfree(ringbuf);
>> +error_unpin_ctx:
>>       if (is_global_default_ctx)
>>           i915_gem_object_ggtt_unpin(ctx_obj);
>>       drm_gem_object_unreference(&ctx_obj->base);
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
>> b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> index a8f72e8..0c4aab1 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> @@ -1721,13 +1721,42 @@ static int init_phys_status_page(struct 
>> intel_engine_cs *ring)
>>       return 0;
>>   }
>>   -void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
>> +void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
>>   {
>> -    if (!ringbuf->obj)
>> -        return;
>> -
>>       iounmap(ringbuf->virtual_start);
>> +    ringbuf->virtual_start = NULL;
>>       i915_gem_object_ggtt_unpin(ringbuf->obj);
>> +}
>> +
>> +int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>> +                     struct intel_ringbuffer *ringbuf)
>> +{
>> +    struct drm_i915_private *dev_priv = to_i915(dev);
>> +    struct drm_i915_gem_object *obj = ringbuf->obj;
>> +    int ret;
>> +
>> +    ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
>> +    if (ret)
>> +        return ret;
>> +
>> +    ret = i915_gem_object_set_to_gtt_domain(obj, true);
>> +    if (ret) {
>> +        i915_gem_object_ggtt_unpin(obj);
>> +        return ret;
>> +    }
>> +
>> +    ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
>> +            i915_gem_obj_ggtt_offset(obj), ringbuf->size);
>> +    if (ringbuf->virtual_start == NULL) {
>> +        i915_gem_object_ggtt_unpin(obj);
>> +        return -EINVAL;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
>> +{
>>       drm_gem_object_unreference(&ringbuf->obj->base);
>>       ringbuf->obj = NULL;
>>   }
>> @@ -1735,12 +1764,7 @@ void intel_destroy_ringbuffer_obj(struct 
>> intel_ringbuffer *ringbuf)
>>   int intel_alloc_ringbuffer_obj(struct drm_device *dev,
>>                      struct intel_ringbuffer *ringbuf)
>>   {
>> -    struct drm_i915_private *dev_priv = to_i915(dev);
>>       struct drm_i915_gem_object *obj;
>> -    int ret;
>> -
>> -    if (ringbuf->obj)
>> -        return 0;
>>         obj = NULL;
>>       if (!HAS_LLC(dev))
>> @@ -1753,30 +1777,9 @@ int intel_alloc_ringbuffer_obj(struct 
>> drm_device *dev,
>>       /* mark ring buffers as read-only from GPU side by default */
>>       obj->gt_ro = 1;
>>   -    ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
>> -    if (ret)
>> -        goto err_unref;
>> -
>> -    ret = i915_gem_object_set_to_gtt_domain(obj, true);
>> -    if (ret)
>> -        goto err_unpin;
>> -
>> -    ringbuf->virtual_start =
>> -        ioremap_wc(dev_priv->gtt.mappable_base + 
>> i915_gem_obj_ggtt_offset(obj),
>> -                ringbuf->size);
>> -    if (ringbuf->virtual_start == NULL) {
>> -        ret = -EINVAL;
>> -        goto err_unpin;
>> -    }
>> -
>>       ringbuf->obj = obj;
>> -    return 0;
>>   -err_unpin:
>> -    i915_gem_object_ggtt_unpin(obj);
>> -err_unref:
>> -    drm_gem_object_unreference(&obj->base);
>> -    return ret;
>> +    return 0;
>>   }
>>     static int intel_init_ring_buffer(struct drm_device *dev,
>> @@ -1813,10 +1816,21 @@ static int intel_init_ring_buffer(struct 
>> drm_device *dev,
>>               goto error;
>>       }
>>   -    ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
>> -    if (ret) {
>> -        DRM_ERROR("Failed to allocate ringbuffer %s: %d\n", 
>> ring->name, ret);
>> -        goto error;
>> +    if (ringbuf->obj == NULL) {
>> +        ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
>> +        if (ret) {
>> +            DRM_ERROR("Failed to allocate ringbuffer %s: %d\n",
>> +                    ring->name, ret);
>> +            goto error;
>> +        }
>> +
>> +        ret = intel_pin_and_map_ringbuffer_obj(dev, ringbuf);
>> +        if (ret) {
>> +            DRM_ERROR("Failed to pin and map ringbuffer %s: %d\n",
>> +                    ring->name, ret);
>> +            intel_destroy_ringbuffer_obj(ringbuf);
>> +            goto error;
>> +        }
>>       }
>>         /* Workaround an erratum on the i830 which causes a hang if
>> @@ -1854,6 +1868,7 @@ void intel_cleanup_ring_buffer(struct 
>> intel_engine_cs *ring)
>>       intel_stop_ring_buffer(ring);
>>       WARN_ON(!IS_GEN2(ring->dev) && (I915_READ_MODE(ring) & 
>> MODE_IDLE) == 0);
>>   +    intel_unpin_ringbuffer_obj(ringbuf);
>>       intel_destroy_ringbuffer_obj(ringbuf);
>>       ring->preallocated_lazy_request = NULL;
>>       ring->outstanding_lazy_seqno = 0;
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h 
>> b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> index 8c002d2..365854ad 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> @@ -382,6 +382,9 @@ intel_write_status_page(struct intel_engine_cs 
>> *ring,
>>   #define I915_GEM_HWS_SCRATCH_INDEX    0x30
>>   #define I915_GEM_HWS_SCRATCH_ADDR (I915_GEM_HWS_SCRATCH_INDEX << 
>> MI_STORE_DWORD_INDEX_SHIFT)
>>   +void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf);
>> +int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>> +                     struct intel_ringbuffer *ringbuf);
>>   void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf);
>>   int intel_alloc_ringbuffer_obj(struct drm_device *dev,
>>                      struct intel_ringbuffer *ringbuf);
>
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