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[142.68.57.212]) by smtp.gmail.com with ESMTPSA id r15sm18535564qtr.40.2020.03.16.05.38.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 16 Mar 2020 05:38:00 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jDp0J-0003bq-Mn; Mon, 16 Mar 2020 09:37:59 -0300 Date: Mon, 16 Mar 2020 09:37:59 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Christian =?utf-8?B?S8O2bmln?= , David1.Zhou@amd.com, daniel@ffwll.ch, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org, Logan Gunthorpe Subject: Re: [PATCH 1/6] lib/scatterlist: add sg_set_dma_addr() function Message-ID: <20200316123759.GC20941@ziepe.ca> References: <20200312101943.GA14618@infradead.org> <20200312104729.GA26031@infradead.org> <20200312141928.GK31668@ziepe.ca> <20200313112139.GA4913@infradead.org> <20200313121742.GZ31668@ziepe.ca> <20200316085642.GC1831@infradead.org> <20200316095213.GA29212@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200316095213.GA29212@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Mon, Mar 16, 2020 at 02:52:13AM -0700, Christoph Hellwig wrote: > On Mon, Mar 16, 2020 at 10:41:42AM +0100, Christian König wrote: > > Well I would prefer if the drivers can somehow express their requirements > > and get IOVA structures already in the form they need. > > > > Converting the IOVA data from one form to another is sometimes quite costly. > > Especially when it is only temporarily needed. > > We basically have two ways to generate the IOVA: > > - a linear translation for the direct mapping case or some dumb IOMMU > drivers - in that case case there is a 1:1 mapping between input > segments and output segments in DMA mapping > - a non-trivial IOMMU where all aligned segments are merged into > a single IOVA range > > So I don't really see how the dma layer could help much with any > limitation beyond existing max size and dma boundary ones. Christian are you thinking of something like the controllable address&flags scheme in hmm_range_fault() so that the dma_map process can write DMA address pages directly to some HW formatted structure? 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[142.68.57.212]) by smtp.gmail.com with ESMTPSA id r15sm18535564qtr.40.2020.03.16.05.38.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 16 Mar 2020 05:38:00 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jDp0J-0003bq-Mn; Mon, 16 Mar 2020 09:37:59 -0300 Date: Mon, 16 Mar 2020 09:37:59 -0300 From: Jason Gunthorpe To: Christoph Hellwig Subject: Re: [PATCH 1/6] lib/scatterlist: add sg_set_dma_addr() function Message-ID: <20200316123759.GC20941@ziepe.ca> References: <20200312101943.GA14618@infradead.org> <20200312104729.GA26031@infradead.org> <20200312141928.GK31668@ziepe.ca> <20200313112139.GA4913@infradead.org> <20200313121742.GZ31668@ziepe.ca> <20200316085642.GC1831@infradead.org> <20200316095213.GA29212@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200316095213.GA29212@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Mailman-Approved-At: Tue, 17 Mar 2020 14:16:40 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Logan Gunthorpe , Christian =?utf-8?B?S8O2bmln?= , linux-media@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" T24gTW9uLCBNYXIgMTYsIDIwMjAgYXQgMDI6NTI6MTNBTSAtMDcwMCwgQ2hyaXN0b3BoIEhlbGx3 aWcgd3JvdGU6Cj4gT24gTW9uLCBNYXIgMTYsIDIwMjAgYXQgMTA6NDE6NDJBTSArMDEwMCwgQ2hy aXN0aWFuIEvDtm5pZyB3cm90ZToKPiA+IFdlbGwgSSB3b3VsZCBwcmVmZXIgaWYgdGhlIGRyaXZl cnMgY2FuIHNvbWVob3cgZXhwcmVzcyB0aGVpciByZXF1aXJlbWVudHMKPiA+IGFuZCBnZXQgSU9W QSBzdHJ1Y3R1cmVzIGFscmVhZHkgaW4gdGhlIGZvcm0gdGhleSBuZWVkLgo+ID4gCj4gPiBDb252 ZXJ0aW5nIHRoZSBJT1ZBIGRhdGEgZnJvbSBvbmUgZm9ybSB0byBhbm90aGVyIGlzIHNvbWV0aW1l cyBxdWl0ZSBjb3N0bHkuCj4gPiBFc3BlY2lhbGx5IHdoZW4gaXQgaXMgb25seSB0ZW1wb3Jhcmls eSBuZWVkZWQuCj4gCj4gV2UgYmFzaWNhbGx5IGhhdmUgdHdvIHdheXMgdG8gZ2VuZXJhdGUgdGhl IElPVkE6Cj4gCj4gICAtIGEgbGluZWFyIHRyYW5zbGF0aW9uIGZvciB0aGUgZGlyZWN0IG1hcHBp bmcgY2FzZSBvciBzb21lIGR1bWIgSU9NTVUKPiAgICAgZHJpdmVycyAtIGluIHRoYXQgY2FzZSBj YXNlIHRoZXJlIGlzIGEgMToxIG1hcHBpbmcgYmV0d2VlbiBpbnB1dAo+ICAgICBzZWdtZW50cyBh bmQgb3V0cHV0IHNlZ21lbnRzIGluIERNQSBtYXBwaW5nCj4gICAtIGEgbm9uLXRyaXZpYWwgSU9N TVUgd2hlcmUgYWxsIGFsaWduZWQgc2VnbWVudHMgYXJlIG1lcmdlZCBpbnRvCj4gICAgIGEgc2lu Z2xlIElPVkEgcmFuZ2UKPiAKPiBTbyBJIGRvbid0IHJlYWxseSBzZWUgaG93IHRoZSBkbWEgbGF5 ZXIgY291bGQgaGVscCBtdWNoIHdpdGggYW55Cj4gbGltaXRhdGlvbiBiZXlvbmQgZXhpc3Rpbmcg bWF4IHNpemUgYW5kIGRtYSBib3VuZGFyeSBvbmVzLgoKQ2hyaXN0aWFuIGFyZSB5b3UgdGhpbmtp bmcgb2Ygc29tZXRoaW5nIGxpa2UgdGhlIGNvbnRyb2xsYWJsZQphZGRyZXNzJmZsYWdzIHNjaGVt ZSBpbiBobW1fcmFuZ2VfZmF1bHQoKSBzbyB0aGF0IHRoZSBkbWFfbWFwIHByb2Nlc3MKY2FuIHdy aXRlIERNQSBhZGRyZXNzIHBhZ2VzIGRpcmVjdGx5IHRvIHNvbWUgSFcgZm9ybWF0dGVkIHN0cnVj dHVyZT8KCkphc29uCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fCmRyaS1kZXZlbCBtYWlsaW5nIGxpc3QKZHJpLWRldmVsQGxpc3RzLmZyZWVkZXNrdG9wLm9y ZwpodHRwczovL2xpc3RzLmZyZWVkZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2RyaS1kZXZl bAo=