[PATCH 2/2] uacce: add uacce module

[zhangfei.gao at foxmail.com]

Hi, Greg

On 2019/8/21 上午12:59, Greg Kroah-Hartman wrote:
> On Tue, Aug 20, 2019 at 09:08:55PM +0800, zhangfei wrote:
>>
>> On 2019/8/15 下午10:13, Greg Kroah-Hartman wrote:
>>> On Wed, Aug 14, 2019 at 05:34:25PM +0800, Zhangfei Gao wrote:
>>>> +int uacce_register(struct uacce *uacce)
>>>> +{
>>>> +	int ret;
>>>> +
>>>> +	if (!uacce->pdev) {
>>>> +		pr_debug("uacce parent device not set\n");
>>>> +		return -ENODEV;
>>>> +	}
>>>> +
>>>> +	if (uacce->flags & UACCE_DEV_NOIOMMU) {
>>>> +		add_taint(TAINT_CRAP, LOCKDEP_STILL_OK);
>>>> +		dev_warn(uacce->pdev,
>>>> +			 "Register to noiommu mode, which export kernel data to user space and may vulnerable to attack");
>>>> +	}
>>> THat is odd, why even offer this feature then if it is a major issue?
>> UACCE_DEV_NOIOMMU maybe confusing here.
>>
>> In this mode, app use ioctl to get dma_handle from dma_alloc_coherent.
> That's odd, why not use the other default apis to do that?
>
>> It does not matter iommu is enabled or not.
>> In case iommu is disabled, it maybe dangerous to kernel, so we added warning here, is it required?
> You should use the other documentated apis for this, don't create your
> own.
I am sorry, not understand here.
Do you mean there is a standard ioctl or standard api in user space, it 
can get dma_handle from dma_alloc_coherent from kernel?

Thanks