Hi

Am 06.04.21 um 11:35 schrieb Christian König:
> Am 06.04.21 um 11:08 schrieb Thomas Zimmermann:
>> Moving the driver-specific mmap code into a GEM object function allows
>> for using DRM helpers for various mmap callbacks.
>>
>> This change resolves several inconsistencies between regular mmap and
>> prime-based mmap. The vm_ops field in vma is now set for all mmap'ed
>> areas. Previously it way only set for regular mmap calls, prime-based
>> mmap used TTM's default vm_ops. The check for kfd_bo has been taken
>> from amdgpu_verify_access(), which is not called any longer and has
>> been removed.
>>
>> As a side effect, amdgpu_ttm_vm_ops and amdgpu_ttm_fault() are now
>> implemented in amdgpu's GEM code.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 46 -------------
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h |  2 -
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c     |  4 +-
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c     | 64 +++++++++++++++++++
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     | 71 ---------------------
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h     |  1 -
>>   6 files changed, 66 insertions(+), 122 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> index e0c4f7c7f1b9..19c5ab08d9ec 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> @@ -42,52 +42,6 @@
>>   #include <linux/pci-p2pdma.h>
>>   #include <linux/pm_runtime.h>
>> -/**
>> - * amdgpu_gem_prime_mmap - &drm_driver.gem_prime_mmap implementation
>> - * @obj: GEM BO
>> - * @vma: Virtual memory area
>> - *
>> - * Sets up a userspace mapping of the BO's memory in the given
>> - * virtual memory area.
>> - *
>> - * Returns:
>> - * 0 on success or a negative error code on failure.
>> - */
>> -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;
>> -
>> -    /* 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;
>> -}
>> -
>>   static int
>>   __dma_resv_make_exclusive(struct dma_resv *obj)
>>   {
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h
>> index 39b5b9616fd8..3e93b9b407a9 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h
>> @@ -31,8 +31,6 @@ struct drm_gem_object 
>> *amdgpu_gem_prime_import(struct drm_device *dev,
>>                           struct dma_buf *dma_buf);
>>   bool amdgpu_dmabuf_is_xgmi_accessible(struct amdgpu_device *adev,
>>                         struct amdgpu_bo *bo);
>> -int amdgpu_gem_prime_mmap(struct drm_gem_object *obj,
>> -              struct vm_area_struct *vma);
>>   extern const struct dma_buf_ops amdgpu_dmabuf_ops;
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> index 76f48f79c70b..e96d2758f4bb 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -1656,7 +1656,7 @@ static const struct file_operations 
>> amdgpu_driver_kms_fops = {
>>       .flush = amdgpu_flush,
>>       .release = drm_release,
>>       .unlocked_ioctl = amdgpu_drm_ioctl,
>> -    .mmap = amdgpu_mmap,
>> +    .mmap = drm_gem_mmap,
>>       .poll = drm_poll,
>>       .read = drm_read,
>>   #ifdef CONFIG_COMPAT
>> @@ -1719,7 +1719,7 @@ static const struct drm_driver amdgpu_kms_driver 
>> = {
>>       .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>>       .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>>       .gem_prime_import = amdgpu_gem_prime_import,
>> -    .gem_prime_mmap = amdgpu_gem_prime_mmap,
>> +    .gem_prime_mmap = drm_gem_prime_mmap,
>>       .name = DRIVER_NAME,
>>       .desc = DRIVER_DESC,
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> index fb7171e5507c..fe93faad05f2 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> @@ -41,6 +41,36 @@
>>   static const struct drm_gem_object_funcs amdgpu_gem_object_funcs;
>> +static vm_fault_t amdgpu_ttm_fault(struct vm_fault *vmf)
> 
> Please name that function amdgpu_gem_fault or amdgpu_gem_object_fault
> 
>> +{
>> +    struct ttm_buffer_object *bo = vmf->vma->vm_private_data;
>> +    vm_fault_t ret;
>> +
>> +    ret = ttm_bo_vm_reserve(bo, vmf);
>> +    if (ret)
>> +        return ret;
>> +
>> +    ret = amdgpu_bo_fault_reserve_notify(bo);
>> +    if (ret)
>> +        goto unlock;
>> +
>> +    ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
>> +                       TTM_BO_VM_NUM_PREFAULT, 1);
>> +    if (ret == VM_FAULT_RETRY && !(vmf->flags & 
>> FAULT_FLAG_RETRY_NOWAIT))
>> +        return ret;
>> +
>> +unlock:
>> +    dma_resv_unlock(bo->base.resv);
>> +    return ret;
>> +}
>> +
>> +static const struct vm_operations_struct amdgpu_ttm_vm_ops = {
>> +    .fault = amdgpu_ttm_fault,
>> +    .open = ttm_bo_vm_open,
>> +    .close = ttm_bo_vm_close,
>> +    .access = ttm_bo_vm_access
>> +};
>> +
>>   static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
>>   {
>>       struct amdgpu_bo *robj = gem_to_amdgpu_bo(gobj);
>> @@ -201,6 +231,38 @@ static void amdgpu_gem_object_close(struct 
>> drm_gem_object *obj,
>>       ttm_eu_backoff_reservation(&ticket, &list);
>>   }
>> +static 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 long asize = amdgpu_bo_size(bo);
>> +
>> +    if (!vma->vm_file)
>> +        return -ENODEV;
>> +
>> +    if (!adev)
>> +        return -ENODEV;
>> +
>> +    /* Check for valid size. */
>> +    if (asize < vma->vm_end - vma->vm_start)
>> +        return -EINVAL;
> 
>> +
>> +    /*
>> +     * Don't verify access for KFD BOs. They don't have a GEM
>> +     * object associated with them.
>> +     */
>> +    if (bo->kfd_bo)
>> +        goto out;
> 
> Who does the access verification now?

This is somewhat confusing.

I took this check as-is, including the comment, from amdgpu's 
verify_access function. The verify_access function was called by 
ttm_bo_mmap. It returned 0 and ttm_bo_mmap did the mapping.

> 
> Christian.
> 
>> +
>> +    if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
>> +        (bo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS)) {
>> +        return -EPERM;
>> +    }
>> +
>> +out:
>> +    return drm_gem_ttm_mmap(obj, vma);
>> +}
>> +
>>   static const struct drm_gem_object_funcs amdgpu_gem_object_funcs = {
>>       .free = amdgpu_gem_object_free,
>>       .open = amdgpu_gem_object_open,
>> @@ -208,6 +270,8 @@ static const struct drm_gem_object_funcs 
>> amdgpu_gem_object_funcs = {
>>       .export = amdgpu_gem_prime_export,
>>       .vmap = drm_gem_ttm_vmap,
>>       .vunmap = drm_gem_ttm_vunmap,
>> +    .mmap = amdgpu_gem_prime_mmap,
>> +    .vm_ops = &amdgpu_ttm_vm_ops,
>>   };
>>   /*
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> index 1c6131489a85..d9de91a517c6 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> @@ -152,32 +152,6 @@ static void amdgpu_evict_flags(struct 
>> ttm_buffer_object *bo,
>>       *placement = abo->placement;
>>   }
>> -/**
>> - * amdgpu_verify_access - Verify access for a mmap call
>> - *
>> - * @bo:    The buffer object to map
>> - * @filp: The file pointer from the process performing the mmap
>> - *
>> - * This is called by ttm_bo_mmap() to verify whether a process
>> - * has the right to mmap a BO to their process space.
>> - */
>> -static int amdgpu_verify_access(struct ttm_buffer_object *bo, struct 
>> file *filp)
>> -{
>> -    struct amdgpu_bo *abo = ttm_to_amdgpu_bo(bo);
>> -
>> -    /*
>> -     * Don't verify access for KFD BOs. They don't have a GEM
>> -     * object associated with them.
>> -     */
>> -    if (abo->kfd_bo)
>> -        return 0;
>> -
>> -    if (amdgpu_ttm_tt_get_usermm(bo->ttm))
>> -        return -EPERM;
>> -    return drm_vma_node_verify_access(&abo->tbo.base.vma_node,
>> -                      filp->private_data);
>> -}

Here's the orignal verification code. It gives a free pass to KFD.

>> -
>>   /**
>>    * amdgpu_ttm_map_buffer - Map memory into the GART windows
>>    * @bo: buffer object to map
>> @@ -1531,7 +1505,6 @@ static struct ttm_device_funcs amdgpu_bo_driver = {
>>       .eviction_valuable = amdgpu_ttm_bo_eviction_valuable,
>>       .evict_flags = &amdgpu_evict_flags,
>>       .move = &amdgpu_bo_move,
>> -    .verify_access = &amdgpu_verify_access,
>>       .delete_mem_notify = &amdgpu_bo_delete_mem_notify,
>>       .release_notify = &amdgpu_bo_release_notify,
>>       .io_mem_reserve = &amdgpu_ttm_io_mem_reserve,
>> @@ -1906,50 +1879,6 @@ void amdgpu_ttm_set_buffer_funcs_status(struct 
>> amdgpu_device *adev, bool enable)
>>       adev->mman.buffer_funcs_enabled = enable;
>>   }
>> -static vm_fault_t amdgpu_ttm_fault(struct vm_fault *vmf)
>> -{
>> -    struct ttm_buffer_object *bo = vmf->vma->vm_private_data;
>> -    vm_fault_t ret;
>> -
>> -    ret = ttm_bo_vm_reserve(bo, vmf);
>> -    if (ret)
>> -        return ret;
>> -
>> -    ret = amdgpu_bo_fault_reserve_notify(bo);
>> -    if (ret)
>> -        goto unlock;
>> -
>> -    ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
>> -                       TTM_BO_VM_NUM_PREFAULT, 1);
>> -    if (ret == VM_FAULT_RETRY && !(vmf->flags & 
>> FAULT_FLAG_RETRY_NOWAIT))
>> -        return ret;
>> -
>> -unlock:
>> -    dma_resv_unlock(bo->base.resv);
>> -    return ret;
>> -}
>> -
>> -static const struct vm_operations_struct amdgpu_ttm_vm_ops = {
>> -    .fault = amdgpu_ttm_fault,
>> -    .open = ttm_bo_vm_open,
>> -    .close = ttm_bo_vm_close,
>> -    .access = ttm_bo_vm_access
>> -};
>> -
>> -int amdgpu_mmap(struct file *filp, struct vm_area_struct *vma)
>> -{
>> -    struct drm_file *file_priv = filp->private_data;
>> -    struct amdgpu_device *adev = drm_to_adev(file_priv->minor->dev);
>> -    int r;
>> -
>> -    r = ttm_bo_mmap(filp, vma, &adev->mman.bdev);
>> -    if (unlikely(r != 0))
>> -        return r;
>> -
>> -    vma->vm_ops = &amdgpu_ttm_vm_ops;
>> -    return 0;
>> -}

And this was the mmap callback in struct file_operations. It calls 
ttm_bo_mmap(), which skips verification for KFD BOs. To the best of my 
knowledge, there was no additional verification for these KFD BOs.

The original code in amdgpu_gem_prime_mmap() did seom verification, but 
didn't handle KFD specially. I guess, PRIME needs GEM and KFD BOs 
wouldn't quailify.

In the end I went with the semantics I found in amdgpu_mmap() and 
handled KFD specially. Let me know if this requires to be changed.

Best regards
Thomas

>> -
>>   int amdgpu_copy_buffer(struct amdgpu_ring *ring, uint64_t src_offset,
>>                  uint64_t dst_offset, uint32_t byte_count,
>>                  struct dma_resv *resv,
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> index dec0db8b0b13..6e51faad7371 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> @@ -146,7 +146,6 @@ int amdgpu_fill_buffer(struct amdgpu_bo *bo,
>>               struct dma_resv *resv,
>>               struct dma_fence **fence);
>> -int amdgpu_mmap(struct file *filp, struct vm_area_struct *vma);
>>   int amdgpu_ttm_alloc_gart(struct ttm_buffer_object *bo);
>>   int amdgpu_ttm_recover_gart(struct ttm_buffer_object *tbo);
>>   uint64_t amdgpu_ttm_domain_start(struct amdgpu_device *adev, 
>> uint32_t type);
> 
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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer