Virtualization - Jul 2021 - [RFC PATCH] vhost-vdpa: mark vhost device invalid to reflect vdpa device unregistration

? 2021/7/5 ??4:52, gautam.dawar at xilinx.com ??:
>   	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> @@ -1091,11 +1122,13 @@ static void vhost_vdpa_remove(struct vdpa_device
*vdpa)
>   		opened = atomic_cmpxchg(&v->opened, 0, 1);
>   		if (!opened)
>   			break;
> -		wait_for_completion_timeout(&v->completion,
> -					    msecs_to_jiffies(1000));
> -		dev_warn_once(&v->dev,
> -			      "%s waiting for/dev/%s to be closed\n",
> -			      __func__, dev_name(&v->dev));
> +		if (!wait_for_completion_timeout(&v->completion,
> +					    msecs_to_jiffies(1000))) {
> +			dev_warn(&v->dev,
> +				 "%s/dev/%s in use, continue..\n",
> +				 __func__, dev_name(&v->dev));
> +			break;
> +		}
>   	} while (1);
>   
>   	put_device(&v->dev);
> +	v->dev_invalid = true;

Besides the mapping handling mentioned by Michael. I think this can lead 
use-after-free. put_device may release the memory.

Another fundamental issue, vDPA is the parent of vhost-vDPA device. I'm 
not sure the device core can allow the parent to go away first.

Thanks

? 2021/7/5 ??11:48, Jason Wang ??:
>
> ? 2021/7/5 ??4:52, gautam.dawar at xilinx.com ??:
>> ????? vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> @@ -1091,11 +1122,13 @@ static void vhost_vdpa_remove(struct 
>> vdpa_device *vdpa)
>> ????????? opened = atomic_cmpxchg(&v->opened, 0, 1);
>> ????????? if (!opened)
>> ????????????? break;
>> -??????? wait_for_completion_timeout(&v->completion,
>> -??????????????????????? msecs_to_jiffies(1000));
>> -??????? dev_warn_once(&v->dev,
>> -????????????????? "%s waiting for/dev/%s to be closed\n",
>> -????????????????? __func__, dev_name(&v->dev));
>> +??????? if (!wait_for_completion_timeout(&v->completion,
>> +??????????????????????? msecs_to_jiffies(1000))) {
>> +??????????? dev_warn(&v->dev,
>> +???????????????? "%s/dev/%s in use, continue..\n",
>> +???????????????? __func__, dev_name(&v->dev));
>> +??????????? break;
>> +??????? }
>> ????? } while (1);
>> ? ????? put_device(&v->dev);
>> +??? v->dev_invalid = true;
>
>
> Besides the mapping handling mentioned by Michael. I think this can 
> lead use-after-free. put_device may release the memory.
>
> Another fundamental issue, vDPA is the parent of vhost-vDPA device. 
> I'm not sure the device core can allow the parent to go away first.

Or this probably means you need couple the fd loosely with the 
vhost-vDPA device.

Thanks

>
> Thanks
>
>