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: <20240923090226.GI11337@unreal>
Date: Mon, 23 Sep 2024 12:02:26 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Junxian Huang <huangjunxian6@...ilicon.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>, 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 Mon, Sep 23, 2024 at 02:17:40PM +0800, Junxian Huang wrote:
> 
> 
> 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.

It is interested claim given the fact that you are changing original
code from 2016.

Thanks

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