linux-kernel - Re: [PATCH rdma-next 1/1] RDMA/mana_ib: indicate that inline data is not supported

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Message-ID: <20240716142223.GC5630@unreal>
Date: Tue, 16 Jul 2024 17:22:23 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Konstantin Taranov <kotaranov@...rosoft.com>
Cc: Konstantin Taranov <kotaranov@...ux.microsoft.com>,
	Wei Hu <weh@...rosoft.com>,
	"sharmaajay@...rosoft.com" <sharmaajay@...rosoft.com>,
	Long Li <longli@...rosoft.com>, "jgg@...pe.ca" <jgg@...pe.ca>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH rdma-next 1/1] RDMA/mana_ib: indicate that inline data is
 not supported

On Tue, Jul 16, 2024 at 01:42:49PM +0000, Konstantin Taranov wrote:
> > > Set max_inline_data to zero during RC QP creation.
> > >
> > > Fixes: fdefb9184962 ("RDMA/mana_ib: Implement uapi to create and
> > > destroy RC QP")
> > > Signed-off-by: Konstantin Taranov <kotaranov@...rosoft.com>
> > > ---
> > >  drivers/infiniband/hw/mana/qp.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/infiniband/hw/mana/qp.c
> > > b/drivers/infiniband/hw/mana/qp.c index 73d67c853b6f..d9f24a763e72
> > > 100644
> > > --- a/drivers/infiniband/hw/mana/qp.c
> > > +++ b/drivers/infiniband/hw/mana/qp.c
> > > @@ -426,6 +426,8 @@ static int mana_ib_create_rc_qp(struct ib_qp *ibqp,
> > struct ib_pd *ibpd,
> > >  	u64 flags = 0;
> > >  	u32 doorbell;
> > >
> > > +	/* inline data is not supported */
> > > +	attr->cap.max_inline_data = 0;
> > 
> > Can you please point to me to the flow where attr is not zeroed before?
> >
> 
> Sorry, I do not understand the question. I cannot point to something that is not in the code.
> 
> It is to support the case when user asks for x bytes inlined
> when it creates a QP, and we respond with actual allowed inline
> data for the created QP. (as defined in: "The function ibv_create_qp()
> will update the qp_init_attr->cap struct with the actual QP values of
> the QP that was created;")
> 
> The kernel logic is inside "static int create_qp(struct uverbs_attr_bundle *attrs, struct ib_uverbs_ex_create_qp *cmd)"
> where we do the following:
> attr.cap.max_inline_data = cmd->max_inline_data;
> qp = ib_create_qp_user(..,&attr,..);

Awesome, ib_create_qp_user() is called exactly in two places, and in
both cases I see this line "struct ib_qp_init_attr attr = {}; "

It means that attr is zeroed.

Thanks

> resp.base.max_inline_data = attr.cap.max_inline_data;
> 
> So, my change makes sure that the response will have 0 and not the value the user asked,
> as we do not support inlining. So without the fix, the user who was asking for inlining was falsely
> seeing that we support it (example of such an application is rdma_server from librdmacm).
> 
> Thanks
> 
> > Thanks
> > 
> > >  	if (!udata || udata->inlen < sizeof(ucmd))
> > >  		return -EINVAL;
> > >
> > > --
> > > 2.43.0
> > >