[PATCH v2] drm/amdkfd: Move dma unmapping after TLB flush

[Felix Kuehling]

On 2023-09-11 15:55, Philip Yang wrote:
> Otherwise GPU may access the stale mapping and generate IOMMU
> IO_PAGE_FAULT.
>
> Move this to inside p->mutex to prevent multiple threads mapping and
> unmapping concurrently race condition.
>
> After kfd_mem_dmaunmap_attachment is removed from unmap_bo_from_gpuvm,
> kfd_mem_dmaunmap_attachment is called if failed to map to GPUs, and
> before free the mem attachment in case failed to unmap from GPUs.
>
> Signed-off-by: Philip Yang <Philip.Yang at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h    |  1 +
>   .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  | 22 +++++++++++++++---
>   drivers/gpu/drm/amd/amdkfd/kfd_chardev.c      | 23 ++++++++++++-------
>   3 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> index 559f14cc0a99..dff79a623f4a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> @@ -304,6 +304,7 @@ int amdgpu_amdkfd_gpuvm_map_memory_to_gpu(struct amdgpu_device *adev,
>   					  struct kgd_mem *mem, void *drm_priv);
>   int amdgpu_amdkfd_gpuvm_unmap_memory_from_gpu(
>   		struct amdgpu_device *adev, struct kgd_mem *mem, void *drm_priv);
> +void amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct amdgpu_vm *vm, struct kgd_mem *mem);

For consistency with the other amdgpu_amdkfd APIs, please replace the vm 
parameter with a drm_priv parameter and do the drm_priv_to_vm 
translation inside amdgpu_amdkfd_gpuvm_dmaunmap_mem.


>   int amdgpu_amdkfd_gpuvm_sync_memory(
>   		struct amdgpu_device *adev, struct kgd_mem *mem, bool intr);
>   int amdgpu_amdkfd_gpuvm_map_gtt_bo_to_kernel(struct kgd_mem *mem,
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index b5b940485059..ae767ad7afa2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -1249,8 +1249,6 @@ static void unmap_bo_from_gpuvm(struct kgd_mem *mem,
>   	amdgpu_vm_clear_freed(adev, vm, &bo_va->last_pt_update);
>   
>   	amdgpu_sync_fence(sync, bo_va->last_pt_update);
> -
> -	kfd_mem_dmaunmap_attachment(mem, entry);
>   }
>   
>   static int update_gpuvm_pte(struct kgd_mem *mem,
> @@ -1305,6 +1303,7 @@ static int map_bo_to_gpuvm(struct kgd_mem *mem,
>   
>   update_gpuvm_pte_failed:
>   	unmap_bo_from_gpuvm(mem, entry, sync);
> +	kfd_mem_dmaunmap_attachment(mem, entry);
>   	return ret;
>   }
>   
> @@ -1910,8 +1909,10 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
>   		mem->va + bo_size * (1 + mem->aql_queue));
>   
>   	/* Remove from VM internal data structures */
> -	list_for_each_entry_safe(entry, tmp, &mem->attachments, list)
> +	list_for_each_entry_safe(entry, tmp, &mem->attachments, list) {
> +		kfd_mem_dmaunmap_attachment(mem, entry);

In theory this should not be needed, because user mode is required to 
unmap all mappings before freeing the BO. If (mapped_to_gpu_memory > 0), 
this function returns -EBUSY. For SG BOs, you may run into this error 
message:

     pr_err("SG Table of BO is UNEXPECTEDLY NULL");

If you decide to leave this dmaunmap_attachment here, you may want to 
turn that error into a pr_debug and remove "UNEXPECTEDLY".

Regards,
   Felix


>   		kfd_mem_detach(entry);
> +	}
>   
>   	ret = unreserve_bo_and_vms(&ctx, false, false);
>   
> @@ -2085,6 +2086,21 @@ int amdgpu_amdkfd_gpuvm_map_memory_to_gpu(
>   	return ret;
>   }
>   
> +void amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct amdgpu_vm *vm, struct kgd_mem *mem)
> +{
> +	struct kfd_mem_attachment *entry;
> +
> +	mutex_lock(&mem->lock);
> +
> +	list_for_each_entry(entry, &mem->attachments, list) {
> +		if (entry->bo_va->base.vm != vm)
> +			continue;
> +		kfd_mem_dmaunmap_attachment(mem, entry);
> +	}
> +
> +	mutex_unlock(&mem->lock);
> +}
> +
>   int amdgpu_amdkfd_gpuvm_unmap_memory_from_gpu(
>   		struct amdgpu_device *adev, struct kgd_mem *mem, void *drm_priv)
>   {
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> index 08687ce0aa8b..645628ff1faf 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> @@ -1432,17 +1432,24 @@ static int kfd_ioctl_unmap_memory_from_gpu(struct file *filep,
>   			goto sync_memory_failed;
>   		}
>   	}
> -	mutex_unlock(&p->mutex);
>   
> -	if (flush_tlb) {
> -		/* Flush TLBs after waiting for the page table updates to complete */
> -		for (i = 0; i < args->n_devices; i++) {
> -			peer_pdd = kfd_process_device_data_by_id(p, devices_arr[i]);
> -			if (WARN_ON_ONCE(!peer_pdd))
> -				continue;
> +	/* Flush TLBs after waiting for the page table updates to complete */
> +	for (i = 0; i < args->n_devices; i++) {
> +		struct amdgpu_vm *vm;
> +
> +		peer_pdd = kfd_process_device_data_by_id(p, devices_arr[i]);
> +		if (WARN_ON_ONCE(!peer_pdd))
> +			continue;
> +		if (flush_tlb)
>   			kfd_flush_tlb(peer_pdd, TLB_FLUSH_HEAVYWEIGHT);
> -		}
> +
> +		/* Remove dma mapping after tlb flush to avoid IO_PAGE_FAULT */
> +		vm = drm_priv_to_vm(peer_pdd->drm_priv);
> +		amdgpu_amdkfd_gpuvm_dmaunmap_mem(vm, mem);
>   	}
> +
> +	mutex_unlock(&p->mutex);
> +
>   	kfree(devices_arr);
>   
>   	return 0;