RE: RE: [EXT] Re: [PATCH v8 rdma-next 4/7] RDMA/siw: Use the common mmap_xa helpers

["Bernard Metzler" <BMT@zurich.ibm.com>]

-----"Michal Kalderon" <mkalderon@marvell.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Michal Kalderon" <mkalderon@marvell.com>
>Date: 09/02/2019 10:01AM
>Cc: "Ariel Elior" <aelior@marvell.com>, "jgg@ziepe.ca"
><jgg@ziepe.ca>, "dledford@redhat.com" <dledford@redhat.com>,
>"galpress@amazon.com" <galpress@amazon.com>, "sleybo@amazon.com"
><sleybo@amazon.com>, "leon@kernel.org" <leon@kernel.org>,
>"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
>Subject: [EXTERNAL] RE: RE: [EXT] Re: [PATCH v8 rdma-next 4/7]
>RDMA/siw: Use the common mmap_xa helpers
>
>> From: linux-rdma-owner@vger.kernel.org <linux-rdma-
>> owner@vger.kernel.org> On Behalf Of Bernard Metzler
>> 
>> -----"Michal Kalderon" <mkalderon@marvell.com> wrote: -----
>> 
>> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >From: "Michal Kalderon" <mkalderon@marvell.com>
>> >Date: 08/30/2019 02:42PM
>> >Cc: "Ariel Elior" <aelior@marvell.com>, "jgg@ziepe.ca"
>> ><jgg@ziepe.ca>, "dledford@redhat.com" <dledford@redhat.com>,
>> >"galpress@amazon.com" <galpress@amazon.com>,
>> "sleybo@amazon.com"
>> ><sleybo@amazon.com>, "leon@kernel.org" <leon@kernel.org>,
>> >"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>, "Ariel
>> >Elior" <aelior@marvell.com>
>> >Subject: [EXTERNAL] RE: [EXT] Re: [PATCH v8 rdma-next 4/7]
>RDMA/siw:
>> >Use the common mmap_xa helpers
>> >
>> >> From: Bernard Metzler <BMT@zurich.ibm.com>
>> >> Sent: Friday, August 30, 2019 3:08 PM
>> >>
>> >> External Email
>> >>
>> >>
>>
>>--------------------------------------------------------------------
>-
>> >-
>> >> -----"Michal Kalderon" <michal.kalderon@marvell.com> wrote:
>-----
>> >>
>> >> Hi Michael,
>> >>
>> >> I tried this patch. It unfortunately panics immediately when siw
>> >gets used. I'll
>> >> investigate further. Some comments in line.
>> >Thanks for testing,
>> >
>> >>
>> >> Thanks
>> >> Bernard.
>> >>
>> >> >To: <mkalderon@marvell.com>, <aelior@marvell.com>,
>> <jgg@ziepe.ca>,
>> >> ><dledford@redhat.com>, <bmt@zurich.ibm.com>,
>> >> <galpress@amazon.com>,
>> >> ><sleybo@amazon.com>, <leon@kernel.org>
>> >> >From: "Michal Kalderon" <michal.kalderon@marvell.com>
>> >> >Date: 08/27/2019 03:31PM
>> >> >Cc: <linux-rdma@vger.kernel.org>, "Michal Kalderon"
>> >> ><michal.kalderon@marvell.com>, "Ariel Elior"
>> >> ><ariel.elior@marvell.com>
>> >> >Subject: [EXTERNAL] [PATCH v8 rdma-next 4/7] RDMA/siw: Use the
>> >> common
>> >> >mmap_xa helpers
>> >> >
>> >> >Remove the functions related to managing the mmap_xa database.
>> >> >This code is now common in ib_core. Use the common API's
>instead.
>> >> >
>> >> >Signed-off-by: Ariel Elior <ariel.elior@marvell.com>
>> >> >Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
>> >> >---
>> >> > drivers/infiniband/sw/siw/siw.h       |  20 ++-
>> >> > drivers/infiniband/sw/siw/siw_main.c  |   1 +
>> >> > drivers/infiniband/sw/siw/siw_verbs.c | 223
>> >> >+++++++++++++++++++---------------
>> >> > drivers/infiniband/sw/siw/siw_verbs.h |   1 +
>> >> > 4 files changed, 144 insertions(+), 101 deletions(-)
>> >> >
>> >> >+			/* If entry was inserted successfully, qp->sendq
>> >> >+			 * will be freed by siw_mmap_free
>> >> >+			 */
>> >> >+			qp->sendq = NULL;
>> >>
>> >> qp->sendq points to the SQ array. Zeroing this pointer will
>leave
>> >> siw with no idea where the WQE's are. It will panic
>de-referencing
>> >[NULL +
>> >> current position in ring buffer]. Same for RQ, SRQ and CQ.
>> >Qp->sendq is only used in kernel mode, and only set to NULL is
>> >user-space mode
>> >Where it is allocated and mapped in user, so the user will be the
>one
>> >accessing the rings And not kernel, unless I'm missing something.
>> 
>> These pointers are pointing to the allocated work queues.
>> These queues/arrays are holding the actual send/recv/complete/srq
>work
>> queue elements. It is a shared array. That is why we need mmap at
>all.
>> 
>> e.g.,
>> 
>> struct siw_sqe *sqe = &qp->sendq[qp->sq_get % qp->attrs.sq_size];
>> 
>> 
>Ok got it, I'm HW oriented... so user chains and kernel are totally
>separated. 
>Will add a flag whether to free or not and remove setting to NULL. 

Forget my last reply. I was under the impression the RDMA core
mmap_xa helper stuff would free the resource. Sorry about that. So
just do not free the resource in siw_mmap_free().

Best regards,
Bernard.