linux-kernel - RE: [EXTERNAL] Re: [Patch v7 5/5] RDMA/mana

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Message-ID: <MN0PR21MB36067E337A53C3BAF8B648E5D6DEA@MN0PR21MB3606.namprd21.prod.outlook.com>
Date:   Wed, 25 Oct 2023 19:59:18 +0000
From:   Ajay Sharma <sharmaajay@...rosoft.com>
To:     Jason Gunthorpe <jgg@...pe.ca>,
        "sharmaajay@...uxonhyperv.com" <sharmaajay@...uxonhyperv.com>
CC:     Long Li <longli@...rosoft.com>, Leon Romanovsky <leon@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ajay Sharma <sharmaajay@...rosoft.com>
Subject: RE: [EXTERNAL] Re: [Patch v7 5/5] RDMA/mana_ib: Send event to qp


> -----Original Message-----
> From: Jason Gunthorpe <jgg@...pe.ca>
> Sent: Monday, October 23, 2023 11:24 AM
> To: sharmaajay@...uxonhyperv.com
> Cc: Long Li <longli@...rosoft.com>; Leon Romanovsky <leon@...nel.org>;
> Dexuan Cui <decui@...rosoft.com>; Wei Liu <wei.liu@...nel.org>; David S.
> Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>;
> Jakub Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; linux-
> rdma@...r.kernel.org; linux-hyperv@...r.kernel.org;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Ajay Sharma
> <sharmaajay@...rosoft.com>
> Subject: [EXTERNAL] Re: [Patch v7 5/5] RDMA/mana_ib: Send event to qp
> 
> On Mon, Oct 16, 2023 at 03:12:02PM -0700,
> sharmaajay@...uxonhyperv.com wrote:
> 
> > diff --git a/drivers/infiniband/hw/mana/qp.c
> > b/drivers/infiniband/hw/mana/qp.c index ef3275ac92a0..19fae28985c3
> > 100644
> > --- a/drivers/infiniband/hw/mana/qp.c
> > +++ b/drivers/infiniband/hw/mana/qp.c
> > @@ -210,6 +210,8 @@ static int mana_ib_create_qp_rss(struct ib_qp
> *ibqp, struct ib_pd *pd,
> >  		wq->id = wq_spec.queue_index;
> >  		cq->id = cq_spec.queue_index;
> >
> > +		xa_store(&mib_dev->rq_to_qp_lookup_table, wq->id, qp,
> GFP_KERNEL);
> > +
> 
> A store with no erase?
> 
> A load with no locking?
> 
> This can't be right
> 
> Jason

This wq->id is assigned from the HW and is guaranteed to be unique. May be I am not following why do we need a lock here. Can you please explain ?
Ajay