From: Michal Kalderon <mkalderon@marvell.com>
To: Gal Pressman <galpress@amazon.com>, Jason Gunthorpe <jgg@ziepe.ca>
Cc: Ariel Elior <aelior@marvell.com>,
"dledford@redhat.com" <dledford@redhat.com>,
"bmt@zurich.ibm.com" <bmt@zurich.ibm.com>,
"sleybo@amazon.com" <sleybo@amazon.com>,
"leon@kernel.org" <leon@kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: RE: [PATCH v11 rdma-next 6/7] RDMA/qedr: Add doorbell overflow recovery support
Date: Mon, 23 Sep 2019 09:37:23 +0000 [thread overview]
Message-ID: <MN2PR18MB318282190B33DD8DEF5E0F2CA1850@MN2PR18MB3182.namprd18.prod.outlook.com> (raw)
In-Reply-To: <82541758-3e72-d485-6923-cf3336a4297a@amazon.com>
> From: linux-rdma-owner@vger.kernel.org <linux-rdma-
> owner@vger.kernel.org> On Behalf Of Gal Pressman
>
> On 20/09/2019 16:38, Jason Gunthorpe wrote:
> > On Fri, Sep 20, 2019 at 04:30:52PM +0300, Gal Pressman wrote:
> >> On 19/09/2019 21:02, Jason Gunthorpe wrote:
> >>> On Thu, Sep 05, 2019 at 01:01:16PM +0300, Michal Kalderon wrote:
> >>>
> >>>> @@ -347,6 +360,9 @@ void qedr_mmap_free(struct
> rdma_user_mmap_entry
> >>>> *rdma_entry) {
> >>>> struct qedr_user_mmap_entry *entry =
> >>>> get_qedr_mmap_entry(rdma_entry);
> >>>>
> >>>> + if (entry->mmap_flag == QEDR_USER_MMAP_PHYS_PAGE)
> >>>> + free_page((unsigned long)phys_to_virt(entry->address));
> >>>> +
> >>>
> >>> While it isn't wrong it do it this way, we don't need this
> >>> mmap_free() stuff for normal CPU pages. Those are refcounted and
> >>> qedr can simply call free_page() during the teardown of the uobject
> >>> that is using the this page. This is what other drivers already do.
> >>
> >> This is pretty much what EFA does as well. When we allocate pages
> >> for the user (CQ for example), we DMA map them and later on mmap
> them
> >> to the user. We expect those pages to remain until the entry is
> >> freed, how can we call free_page, who is holding a refcount on those
> >> except for the driver?
> >
> > free_page is kind of a lie, it is more like put_page (see
> > __free_pages). I think the difference is that it assumes the page came
> > from alloc_page and skips some generic stuff when freeing it.
> >
> > When the driver does vm_insert_page the vma holds another refcount and
> > the refcount does not go to zero until that page drops out of the vma
> > (ie at the same time mmap_free above is called).
> >
> > Then __put_page will do the free_unref_page(), etc.
> >
> > So for CPU pages it is fine to not use mmap_free so long as
> > vm_insert_page is used
>
> Thanks, I did not know this, it simplifies things.
> In that case, maybe the mmap_free callback is redundant.
We still need it to free the entry though - right ?
Gal, where do you free your hardware resources ?
next prev parent reply other threads:[~2019-09-23 9:37 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 10:01 [PATCH v11 rdma-next 0/7] RDMA/qedr: Use the doorbell overflow recovery mechanism for RDMA Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 1/7] RDMA/core: Move core content from ib_uverbs to ib_core Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 2/7] RDMA/core: Create mmap database and cookie helper functions Michal Kalderon
2019-09-19 17:14 ` Jason Gunthorpe
2019-09-19 17:48 ` Jason Gunthorpe
2019-09-19 18:07 ` Jason Gunthorpe
2019-09-23 9:36 ` [EXT] " Michal Kalderon
2019-09-23 13:30 ` Jason Gunthorpe
2019-09-24 8:31 ` Michal Kalderon
2019-09-24 12:37 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 3/7] RDMA/efa: Use the common mmap_xa helpers Michal Kalderon
2019-09-19 17:37 ` Jason Gunthorpe
2019-09-23 9:15 ` Michal Kalderon
2019-09-23 13:28 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 4/7] RDMA/siw: " Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 5/7] RDMA/qedr: Use the common mmap API Michal Kalderon
2019-09-19 17:55 ` Jason Gunthorpe
2019-09-20 13:39 ` Gal Pressman
2019-09-23 9:21 ` Michal Kalderon
2019-09-23 13:29 ` Jason Gunthorpe
2019-09-24 8:25 ` [EXT] " Michal Kalderon
2019-09-24 8:49 ` Pressman, Gal
2019-09-24 9:31 ` Michal Kalderon
2019-10-20 7:19 ` Gal Pressman
2019-10-21 17:33 ` Jason Gunthorpe
2019-10-23 6:40 ` Gal Pressman
2019-10-23 14:41 ` Jason Gunthorpe
2019-10-24 8:06 ` Gal Pressman
2019-09-05 10:01 ` [PATCH v11 rdma-next 6/7] RDMA/qedr: Add doorbell overflow recovery support Michal Kalderon
2019-09-19 18:02 ` Jason Gunthorpe
2019-09-20 13:30 ` Gal Pressman
2019-09-20 13:38 ` Jason Gunthorpe
2019-09-20 14:00 ` Gal Pressman
2019-09-23 9:37 ` Michal Kalderon [this message]
2019-09-25 19:16 ` [EXT] " Michal Kalderon
2019-09-25 19:21 ` Jason Gunthorpe
2019-09-25 19:37 ` Michal Kalderon
2019-09-26 19:10 ` Jason Gunthorpe
2019-09-23 9:30 ` Michal Kalderon
2019-09-23 13:26 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 7/7] RDMA/qedr: Add iWARP doorbell " Michal Kalderon
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