[PATCH] drm/amdkfd: svm ranges creation for unregistered memory

[Felix Kuehling]

Am 2021-04-19 um 9:52 p.m. schrieb Alex Sierra:
> SVM ranges are created for unregistered memory, triggered
> by page faults. These ranges are migrated/mapped to
> GPU VRAM memory.
>
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>

This looks generally good to me. One more nit-pick inline in addition to
Philip's comments. And one question.


> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 103 ++++++++++++++++++++++++++-
>  1 file changed, 101 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index 45dd055118eb..a8a92c533cf7 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -2179,6 +2179,84 @@ svm_range_best_restore_location(struct svm_range *prange,
>  
>  	return -1;
>  }
> +static int
> +svm_range_get_range_boundaries(struct kfd_process *p, int64_t addr,
> +				unsigned long *start, unsigned long *last)
> +{
> +	struct vm_area_struct *vma;
> +	struct interval_tree_node *node;
> +	unsigned long start_limit, end_limit;
> +
> +	vma = find_vma(p->mm, addr);
> +	if (!vma || addr < vma->vm_start) {
> +		pr_debug("VMA does not exist in address [0x%llx]\n", addr);
> +		return -EFAULT;
> +	}
> +	start_limit = max(vma->vm_start,
> +			(unsigned long)ALIGN_DOWN(addr, 2UL << 20)) >> PAGE_SHIFT;
> +	end_limit = min(vma->vm_end,
> +			(unsigned long)ALIGN(addr + 1, 2UL << 20)) >> PAGE_SHIFT;
> +	/* First range that starts after the fault address */
> +	node = interval_tree_iter_first(&p->svms.objects, (addr >> PAGE_SHIFT) + 1, ULONG_MAX);
> +	if (node) {
> +		end_limit = min(end_limit, node->start);
> +		/* Last range that ends before the fault address */
> +		node = container_of(rb_prev(&node->rb), struct interval_tree_node, rb);
> +	} else {
> +		/* Last range must end before addr because there was no range after addr */
> +		node = container_of(rb_last(&p->svms.objects.rb_root),
> +				    struct interval_tree_node, rb);
> +	}
> +	if (node)
> +		start_limit = max(start_limit, node->last + 1);
> +
> +	*start = start_limit;
> +	*last = end_limit - 1;
> +
> +	pr_debug("vma start: %lx start: %lx vma end: %lx last: %lx\n",
> +		  vma->vm_start >> PAGE_SHIFT, *start,
> +		  vma->vm_end >> PAGE_SHIFT, *last);
> +
> +	return 0;
> +
> +}
> +static struct
> +svm_range *svm_range_create_unregistered_range(struct amdgpu_device *adev,
> +						struct kfd_process *p,
> +						struct mm_struct *mm,
> +						int64_t addr)
> +{
> +	struct svm_range *prange = NULL;
> +	struct svm_range_list *svms;
> +	unsigned long start, last;
> +	uint32_t gpuid, gpuidx;
> +
> +	if (svm_range_get_range_boundaries(p, addr << PAGE_SHIFT,
> +					   &start, &last))
> +		return NULL;
> +
> +	svms = &p->svms;
> +	prange = svm_range_new(&p->svms, start, last);
> +	if (!prange) {
> +		pr_debug("Failed to create prange in address [0x%llx]\\n", addr);
> +		goto out;

You can just return here, since you're not doing any cleanup at the out:
label.


> +	}
> +	if (kfd_process_gpuid_from_kgd(p, adev, &gpuid, &gpuidx)) {
> +		pr_debug("failed to get gpuid from kgd\n");
> +		svm_range_free(prange);
> +		prange = NULL;
> +		goto out;

Just return.


> +	}
> +	prange->preferred_loc = gpuid;
> +	prange->actual_loc = 0;
> +	/* Gurantee prange is migrate it */
> +	prange->validate_timestamp -= AMDGPU_SVM_RANGE_RETRY_FAULT_PENDING;

Is this really specific to svm_range_create_unregistered_range? Or
should we always do this in svm_range_new to guarantee that new ranges
can get validated?

Regards,
  Felix


> +	svm_range_add_to_svms(prange);
> +	svm_range_add_notifier_locked(mm, prange);
> +
> +out:
> +	return prange;
> +}
>  
>  /* svm_range_skip_recover - decide if prange can be recovered
>   * @prange: svm range structure
> @@ -2228,6 +2306,7 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
>  	struct kfd_process *p;
>  	uint64_t timestamp;
>  	int32_t best_loc, gpuidx;
> +	bool write_locked = false;
>  	int r = 0;
>  
>  	p = kfd_lookup_process_by_pasid(pasid);
> @@ -2251,14 +2330,34 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
>  	}
>  
>  	mmap_read_lock(mm);
> +retry_write_locked:
>  	mutex_lock(&svms->lock);
>  	prange = svm_range_from_addr(svms, addr, NULL);
>  	if (!prange) {
>  		pr_debug("failed to find prange svms 0x%p address [0x%llx]\n",
>  			 svms, addr);
> -		r = -EFAULT;
> -		goto out_unlock_svms;
> +		if (!write_locked) {
> +			/* Need the write lock to create new range with MMU notifier.
> +			 * Also flush pending deferred work to make sure the interval
> +			 * tree is up to date before we add a new range
> +			 */
> +			mutex_unlock(&svms->lock);
> +			mmap_read_unlock(mm);
> +			svm_range_list_lock_and_flush_work(svms, mm);
> +			write_locked = true;
> +			goto retry_write_locked;
> +		}
> +		prange = svm_range_create_unregistered_range(adev, p, mm, addr);
> +		if (!prange) {
> +			pr_debug("failed to create unregisterd range svms 0x%p address [0x%llx]\n",
> +			svms, addr);
> +			mmap_write_downgrade(mm);
> +			r = -EFAULT;
> +			goto out_unlock_svms;
> +		}
>  	}
> +	if (write_locked)
> +		mmap_write_downgrade(mm);
>  
>  	mutex_lock(&prange->migrate_mutex);
>