linux-kernel - Re: [PATCH v5 for-next 2/2] RDMA/hns: Disassociate mmap pages for all uctx when HW is being reset

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Message-ID: <24e9ec1c-8b63-f3e0-a465-80030ea6002d@hisilicon.com>
Date: Mon, 23 Sep 2024 14:17:40 +0800
From: Junxian Huang <huangjunxian6@...ilicon.com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Leon Romanovsky <leon@...nel.org>, <linux-rdma@...r.kernel.org>,
	<linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 for-next 2/2] RDMA/hns: Disassociate mmap pages for all
 uctx when HW is being reset



On 2024/9/20 20:47, Jason Gunthorpe wrote:
> On Fri, Sep 20, 2024 at 05:18:14PM +0800, Junxian Huang wrote:
> 
>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_main.c b/drivers/infiniband/hw/hns/hns_roce_main.c
>>>> index 4cb0af733587..49315f39361d 100644
>>>> --- a/drivers/infiniband/hw/hns/hns_roce_main.c
>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_main.c
>>>> @@ -466,6 +466,11 @@ static int hns_roce_mmap(struct ib_ucontext *uctx, struct vm_area_struct *vma)
>>>>  	pgprot_t prot;
>>>>  	int ret;
>>>>  
>>>> +	if (hr_dev->dis_db) {
>>>
>>> How do you clear dis_db after calling to hns_roce_hw_v2_reset_notify_down()? Does it have any locking protection?
>>>
>>
>> Sorry for the late response, I just came back from vacation.
>>
>> After calling hns_roce_hw_v2_reset_notify_down(), we will call ib_unregister_device()
>> and destory all HW resources eventually, so there is no need to clear dis_db.
> 
> Why can't you do the unregister device sooner then and avoid all this
> special stuff?
> 

It's a limitation of HW. Resources such as QP/CQ/MR will be destoryed
during unregistering device. This is not allowed by HW until
hns_roce_hw_v2_reset_notify_uninit(), or it may lead to some HW errors.

> I assumed you'd bring the same device back after completing the reset??
> 

Yes

> Jason