[PATCH v2 1/1] drm/amdgpu: Add gem_prime_mmap support
Christian König
christian.koenig at amd.com
Wed Sep 20 16:20:45 UTC 2017
Am 20.09.2017 um 17:44 schrieb Li, Samuel:
>> What happens when another thread is using amdgpu_dmabuf_ops to call
>> begin_cpu_access/end_cpu_access when you are fixing it up again?
> Right, that is an issue.
A simple "if (!amdgpu_dmabuf_ops.begin_cpu_access)" should be able to
deal with that.
>
>> I would just completely drop the two callbacks, pinning is not necessary for
>> CPU access and thinking more about it it actually has some unwanted side
>> effects.
> CPU access needs synchronization anyway, so the two callbacks cannot be dropped (other drivers implemented too), so I would like to keep it there for now.
Wait a second what do you mean with "CPU access needs synchronization"?
At least i915 makes the memory GPU inaccessible when you start to use it
with the CPU.
If that is what this callback should do then this implementation would
be incorrect. Pinning doesn't wait for any GPU operation to finish.
Regards,
Christian.
>
> Sam
>
>
>> -----Original Message-----
>> From: Koenig, Christian
>> Sent: Wednesday, September 20, 2017 2:58 AM
>> To: Li, Samuel <Samuel.Li at amd.com>; amd-gfx at lists.freedesktop.org
>> Subject: Re: [PATCH v2 1/1] drm/amdgpu: Add gem_prime_mmap support
>>
>>> What do you mean "This isn't race free"?
>> Take a look at the code again:
>>> + dma_buf = drm_gem_prime_export(dev, gobj, flags);
>>> + amdgpu_dmabuf_ops = *(dma_buf->ops);
>>> + amdgpu_dmabuf_ops.begin_cpu_access =
>> amdgpu_gem_begin_cpu_access;
>>> + amdgpu_dmabuf_ops.end_cpu_access =
>> amdgpu_gem_end_cpu_access;
>>> + dma_buf->ops = &amdgpu_dmabuf_ops;
>> What happens when another thread is using amdgpu_dmabuf_ops to call
>> begin_cpu_access/end_cpu_access when you are fixing it up again?
>>
>> I would just completely drop the two callbacks, pinning is not necessary for
>> CPU access and thinking more about it it actually has some unwanted side
>> effects.
>>
>> Regards,
>> Christian.
>>
>> Am 19.09.2017 um 23:22 schrieb Samuel Li:
>>>>> + vma->vm_pgoff = amdgpu_bo_mmap_offset(bo) >> PAGE_SHIFT;
>>>> Maybe better use "vma->vm_pgoff += amdgpu_bo_mmap_offset(bo) >>
>> PAGE_SHIFT;", but I'm not sure.
>>>> How other drivers handle this?
>>> This is a good catch. Looks like pgoff is honored during prime mmap, not a
>> fake offset here.
>>>>> + dma_buf->ops = &amdgpu_dmabuf_ops;
>>>> This isn't race free and needs to be fixed.
>>>> Better add callbacks to drm_prime.c similar to
>> drm_gem_dmabuf_mmap().
>>> What do you mean "This isn't race free"?
>>>
>>> Regards,
>>> Sam
>>>
>>>
>>>
>>> On 2017-09-15 11:05 AM, Christian König wrote:
>>>> Am 14.09.2017 um 00:39 schrieb Samuel Li:
>>>>> v2: drop hdp invalidate/flush.
>>>>>
>>>>> Signed-off-by: Samuel Li <Samuel.Li at amd.com>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 3 ++
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 +-
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c | 77
>> ++++++++++++++++++++++++++++++-
>>>>> 3 files changed, 81 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> index d2aaad7..188b705 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> @@ -395,11 +395,14 @@ amdgpu_gem_prime_import_sg_table(struct
>> drm_device *dev,
>>>>> struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>>>>> struct drm_gem_object *gobj,
>>>>> int flags);
>>>>> +struct drm_gem_object *amdgpu_gem_prime_import(struct
>> drm_device *dev,
>>>>> + struct dma_buf *dma_buf);
>>>>> int amdgpu_gem_prime_pin(struct drm_gem_object *obj);
>>>>> void amdgpu_gem_prime_unpin(struct drm_gem_object *obj);
>>>>> struct reservation_object *amdgpu_gem_prime_res_obj(struct
>> drm_gem_object *);
>>>>> void *amdgpu_gem_prime_vmap(struct drm_gem_object *obj);
>>>>> void amdgpu_gem_prime_vunmap(struct drm_gem_object *obj, void
>>>>> *vaddr);
>>>>> +int amdgpu_gem_prime_mmap(struct drm_gem_object *obj, struct
>>>>> +vm_area_struct *vma);
>>>>> int amdgpu_gem_debugfs_init(struct amdgpu_device *adev);
>>>>> /* sub-allocation manager, it has to be protected by another lock.
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> index 2cdf844..9b63ac5 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> @@ -835,7 +835,7 @@ static struct drm_driver kms_driver = {
>>>>> .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>>>>> .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>>>>> .gem_prime_export = amdgpu_gem_prime_export,
>>>>> - .gem_prime_import = drm_gem_prime_import,
>>>>> + .gem_prime_import = amdgpu_gem_prime_import,
>>>>> .gem_prime_pin = amdgpu_gem_prime_pin,
>>>>> .gem_prime_unpin = amdgpu_gem_prime_unpin,
>>>>> .gem_prime_res_obj = amdgpu_gem_prime_res_obj, @@ -843,6
>>>>> +843,7 @@ static struct drm_driver kms_driver = {
>>>>> .gem_prime_import_sg_table =
>> amdgpu_gem_prime_import_sg_table,
>>>>> .gem_prime_vmap = amdgpu_gem_prime_vmap,
>>>>> .gem_prime_vunmap = amdgpu_gem_prime_vunmap,
>>>>> + .gem_prime_mmap = amdgpu_gem_prime_mmap,
>>>>> .name = DRIVER_NAME,
>>>>> .desc = DRIVER_DESC,
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>> index 5b3f928..13c977a 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>> @@ -57,6 +57,40 @@ void amdgpu_gem_prime_vunmap(struct
>> drm_gem_object *obj, void *vaddr)
>>>>> ttm_bo_kunmap(&bo->dma_buf_vmap);
>>>>> }
>>>>> +int amdgpu_gem_prime_mmap(struct drm_gem_object *obj, struct
>>>>> vm_area_struct *vma)
>>>>> +{
>>>>> + struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
>>>>> + struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>>>>> + unsigned asize = amdgpu_bo_size(bo);
>>>>> + int ret;
>>>>> +
>>>>> + if (!vma->vm_file)
>>>>> + return -ENODEV;
>>>>> +
>>>>> + if (adev == NULL)
>>>>> + return -ENODEV;
>>>>> +
>>>>> + /* Check for valid size. */
>>>>> + if (asize < vma->vm_end - vma->vm_start)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
>>>>> + (bo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS)) {
>>>>> + return -EPERM;
>>>>> + }
>>>>> + vma->vm_pgoff = amdgpu_bo_mmap_offset(bo) >> PAGE_SHIFT;
>>>> Maybe better use "vma->vm_pgoff += amdgpu_bo_mmap_offset(bo) >>
>> PAGE_SHIFT;", but I'm not sure.
>>>> How other drivers handle this?
>>>>
>>>>> +
>>>>> + /* prime mmap does not need to check access, so allow here */
>>>>> + ret = drm_vma_node_allow(&obj->vma_node, vma->vm_file-
>>> private_data);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = ttm_bo_mmap(vma->vm_file, vma, &adev->mman.bdev);
>>>>> + drm_vma_node_revoke(&obj->vma_node,
>>>>> + vma->vm_file->private_data);
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> struct drm_gem_object *
>>>>> amdgpu_gem_prime_import_sg_table(struct drm_device *dev,
>>>>> struct dma_buf_attachment *attach, @@ -130,14
>>>>> +164,55 @@ struct reservation_object
>> *amdgpu_gem_prime_res_obj(struct drm_gem_object *obj)
>>>>> return bo->tbo.resv;
>>>>> }
>>>>> +static int amdgpu_gem_begin_cpu_access(struct dma_buf *dma_buf,
>>>>> enum dma_data_direction direction)
>>>>> +{
>>>>> + return amdgpu_gem_prime_pin(dma_buf->priv);
>>>>> +}
>>>>> +
>>>>> +static int amdgpu_gem_end_cpu_access(struct dma_buf *dma_buf,
>> enum
>>>>> +dma_data_direction direction) {
>>>>> + amdgpu_gem_prime_unpin(dma_buf->priv);
>>>>> +
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> +static struct dma_buf_ops amdgpu_dmabuf_ops;
>>>>> +
>>>>> struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>>>>> struct drm_gem_object *gobj,
>>>>> int flags)
>>>>> {
>>>>> struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
>>>>> + struct dma_buf *dma_buf;
>>>>> if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm))
>>>>> return ERR_PTR(-EPERM);
>>>>> - return drm_gem_prime_export(dev, gobj, flags);
>>>>> + dma_buf = drm_gem_prime_export(dev, gobj, flags);
>>>>> + amdgpu_dmabuf_ops = *(dma_buf->ops);
>>>>> + amdgpu_dmabuf_ops.begin_cpu_access =
>> amdgpu_gem_begin_cpu_access;
>>>>> + amdgpu_dmabuf_ops.end_cpu_access =
>> amdgpu_gem_end_cpu_access;
>>>>> + dma_buf->ops = &amdgpu_dmabuf_ops;
>>>> This isn't race free and needs to be fixed.
>>>>
>>>> Better add callbacks to drm_prime.c similar to
>> drm_gem_dmabuf_mmap().
>>>> Alternative you could just completely drop
>> amdgpu_gem_begin_cpu_access() and amdgpu_gem_end_cpu_access() as
>> well.
>>>> When the buffer is shared between device it is pinned anyway and when
>> it isn't shared ttm_bo_mmap() is able to handle VRAM mappings as well.
>>>> Regards,
>>>> Christian.
>>>>
>>>>> +
>>>>> + return dma_buf;
>>>>> +}
>>>>> +
>>>>> +struct drm_gem_object *amdgpu_gem_prime_import(struct
>> drm_device *dev,
>>>>> + struct dma_buf *dma_buf) {
>>>>> + struct drm_gem_object *obj;
>>>>> +
>>>>> + if (dma_buf->ops == &amdgpu_dmabuf_ops) {
>>>>> + obj = dma_buf->priv;
>>>>> + if (obj->dev == dev) {
>>>>> + /*
>>>>> + * Importing dmabuf exported from out own gem increases
>>>>> + * refcount on gem itself instead of f_count of dmabuf.
>>>>> + */
>>>>> + drm_gem_object_get(obj);
>>>>> + return obj;
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + return drm_gem_prime_import(dev, dma_buf);
>>>>> }
More information about the amd-gfx
mailing list