[PATCH] drm/amdkfd: avoid conflicting address mappings

Felix Kuehling felix.kuehling at amd.com
Thu Jul 15 23:09:15 UTC 2021


On 2021-07-15 3:59 p.m., Alex Sierra wrote:
> [Why]
> Avoid conflict with address ranges mapped by SVM
> mechanism that try to be allocated again through
> ioctl_alloc in the same process. And viceversa.
>
> [How]
> For ioctl_alloc_memory_of_gpu allocations
> Check if the address range passed into ioctl memory
> alloc does not exist already in the kfd_process
> svms->objects interval tree.
>
> For SVM allocations
> Look for the address range into the interval tree VA from
> the VM inside of each pdds used in a kfd_process.
>
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 13 +++++
>   drivers/gpu/drm/amd/amdkfd/kfd_svm.c     | 68 ++++++++++++++++++------
>   2 files changed, 66 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> index 67541c30327a..f39baaa22a62 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> @@ -1251,6 +1251,7 @@ static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
>   	struct kfd_process_device *pdd;
>   	void *mem;
>   	struct kfd_dev *dev;
> +	struct svm_range_list *svms = &p->svms;
>   	int idr_handle;
>   	long err;
>   	uint64_t offset = args->mmap_offset;
> @@ -1259,6 +1260,18 @@ static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
>   	if (args->size == 0)
>   		return -EINVAL;
>   
> +#if IS_ENABLED(CONFIG_HSA_AMD_SVM)
> +	mutex_lock(&svms->lock);
> +	if (interval_tree_iter_first(&svms->objects,
> +				     args->va_addr >> PAGE_SHIFT,
> +				     (args->va_addr + args->size - 1) >> PAGE_SHIFT)) {
> +		pr_err("Address: 0x%llx already allocated by SVM\n",
> +			args->va_addr);
> +		mutex_unlock(&svms->lock);
> +		return -EADDRINUSE;
> +	}
> +	mutex_unlock(&svms->lock);
> +#endif
>   	dev = kfd_device_by_id(args->gpu_id);
>   	if (!dev)
>   		return -EINVAL;
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index 31f3f24cef6a..43b31f00951a 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -2581,9 +2581,46 @@ int svm_range_list_init(struct kfd_process *p)
>   	return 0;
>   }
>   
> +/**
> + * svm_range_is_vm_bo_mapped - check if virtual address range mapped already
> + * @p: current kfd_process
> + * @start: range start address, in pages
> + * @last: range last address, in pages
> + *
> + * The purpose is to avoid virtual address ranges already allocated by
> + * kfd_ioctl_alloc_memory_of_gpu ioctl.
> + * It looks for each pdd in the kfd_process.
> + *
> + * Context: Process context
> + *
> + * Return 0 - OK, if the range is not mapped.
> + * Otherwise error code:
> + * -EADDRINUSE - if address is mapped already by kfd_ioctl_alloc_memory_of_gpu
> + * -EFAULT - if VM does not exist in specific pdd
> + */
> +static int
> +svm_range_is_vm_bo_mapped(struct kfd_process *p, uint64_t start, uint64_t last)
> +{
> +	uint32_t i;
> +
> +	for (i = 0; i < p->n_pdds; i++) {
> +		struct amdgpu_vm *vm = drm_priv_to_vm(p->pdds[i]->drm_priv);
> +
> +		if (!vm)
> +			return -EFAULT;

This is not necessarily an error. Not every process uses every GPU. I 
think you can just skip PDDs that don't have a VM. But you also need a 
NULL-check for p->pdds[i]->drm_priv. I believe it will be NULL on an 
unused GPU (where user mode never called kfd_ioctl_acquire_vm).


> +
> +		if (interval_tree_iter_first(&vm->va, start, last)) {

I believe access to this interval tree needs to happen under the page 
table reservation lock. That means you need to 
amdgpu_bo_reserve(vm->root.bo, false) (and handle the special case that 
it returns -ERESTARTSYS).


> +			pr_debug("Range [0x%llx 0x%llx] already mapped\n", start, last);
> +			return -EADDRINUSE;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>   /**
>    * svm_range_is_valid - check if virtual address range is valid
> - * @mm: current process mm_struct
> + * @mm: current kfd_process
>    * @start: range start address, in pages
>    * @size: range size, in pages
>    *
> @@ -2592,28 +2629,27 @@ int svm_range_list_init(struct kfd_process *p)
>    * Context: Process context
>    *
>    * Return:
> - *  true - valid svm range
> - *  false - invalid svm range
> + *  0 - OK, otherwise error code
>    */
> -static bool
> -svm_range_is_valid(struct mm_struct *mm, uint64_t start, uint64_t size)
> +static int
> +svm_range_is_valid(struct kfd_process *p, uint64_t start, uint64_t size)
>   {
>   	const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
>   	struct vm_area_struct *vma;
>   	unsigned long end;
> +	unsigned long start_unchg = start;
>   
>   	start <<= PAGE_SHIFT;
>   	end = start + (size << PAGE_SHIFT);
> -
>   	do {
> -		vma = find_vma(mm, start);
> +		vma = find_vma(p->mm, start);
>   		if (!vma || start < vma->vm_start ||
>   		    (vma->vm_flags & device_vma))
> -			return false;
> +			return -EFAULT;
>   		start = min(end, vma->vm_end);
>   	} while (start < end);
>   
> -	return true;
> +	return svm_range_is_vm_bo_mapped(p, start_unchg, (end - 1) >> PAGE_SHIFT);
>   }
>   
>   /**
> @@ -2913,9 +2949,9 @@ svm_range_set_attr(struct kfd_process *p, uint64_t start, uint64_t size,
>   
>   	svm_range_list_lock_and_flush_work(svms, mm);
>   
> -	if (!svm_range_is_valid(mm, start, size)) {
> -		pr_debug("invalid range\n");
> -		r = -EFAULT;
> +	r = svm_range_is_valid(p, start, size);
> +	if (r) {
> +		pr_debug("invalid range r=%d\n", r);
>   		mmap_write_unlock(mm);
>   		goto out;
>   	}
> @@ -3016,15 +3052,17 @@ svm_range_get_attr(struct kfd_process *p, uint64_t start, uint64_t size,
>   	uint32_t flags = 0xffffffff;
>   	int gpuidx;
>   	uint32_t i;
> +	int r = 0;
>   
>   	pr_debug("svms 0x%p [0x%llx 0x%llx] nattr 0x%x\n", &p->svms, start,
>   		 start + size - 1, nattr);
>   
>   	mmap_read_lock(mm);
> -	if (!svm_range_is_valid(mm, start, size)) {
> -		pr_debug("invalid range\n");
> +	r = svm_range_is_valid(p, start, size);
> +	if (r) {
> +		pr_debug("invalid range r=%d\n", r);
>   		mmap_read_unlock(mm);

If you move the mmap_read_unlock before the if (r), you don't need to 
duplicate it inside and outside the "if".

Regards,
   Felix


> -		return -EINVAL;
> +		return r;
>   	}
>   	mmap_read_unlock(mm);
>   


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