Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Wed, 18 May 2022 13:05:25 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Ajay Sharma <sharmaajay@microsoft.com>
Cc:     Long Li <longli@microsoft.com>, KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Leon Romanovsky <leon@kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH 05/12] net: mana: Set the DMA device max
 page size
Message-ID: <20220518160525.GP63055@ziepe.ca>
References: <1652778276-2986-1-git-send-email-longli@linuxonhyperv.com>
 <1652778276-2986-6-git-send-email-longli@linuxonhyperv.com>
 <20220517145949.GH63055@ziepe.ca>
 <PH7PR21MB3263EFA8F624F681C3B57636CECE9@PH7PR21MB3263.namprd21.prod.outlook.com>
 <20220517193515.GN63055@ziepe.ca>
 <PH7PR21MB3263C44368F02B8AF8521C4ACECE9@PH7PR21MB3263.namprd21.prod.outlook.com>
 <20220518000356.GO63055@ziepe.ca>
 <BL1PR21MB3283790E8270ED6C639AAB0DD6D19@BL1PR21MB3283.namprd21.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <BL1PR21MB3283790E8270ED6C639AAB0DD6D19@BL1PR21MB3283.namprd21.prod.outlook.com>
Precedence: bulk

On Wed, May 18, 2022 at 05:59:00AM +0000, Ajay Sharma wrote:
> Thanks Long. 
> Hello Jason,
> I am the author of the patch.
> To your comment below : 
> " As I've already said, you are supposed to set the value that limits to ib_sge and *NOT* the value that is related to ib_umem_find_best_pgsz. It is usually 2G because the ib_sge's typically work on a 32 bit length."
> 
> The ib_sge is limited by the __sg_alloc_table_from_pages() which
> uses ib_dma_max_seg_size() which is what is set by the eth driver
> using dma_set_max_seg_size() . Currently our hw does not support
> PTEs larger than 2M.

*sigh* again it has nothing to do with *PTEs* in the HW.

Jason