From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754751AbeDPMjl (ORCPT ); Mon, 16 Apr 2018 08:39:41 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51800 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753745AbeDPMjj (ORCPT ); Mon, 16 Apr 2018 08:39:39 -0400 Date: Mon, 16 Apr 2018 05:39:37 -0700 From: Christoph Hellwig To: Jerome Glisse , christian.koenig@amd.com, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/8] dma-buf: add peer2peer flag Message-ID: <20180416123937.GA9073@infradead.org> References: <20180325110000.2238-1-christian.koenig@amd.com> <20180325110000.2238-4-christian.koenig@amd.com> <20180329065753.GD3881@phenom.ffwll.local> <8b823458-8bdc-3217-572b-509a28aae742@gmail.com> <20180403090909.GN3881@phenom.ffwll.local> <20180403170645.GB5935@redhat.com> <20180403180832.GZ3881@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180403180832.GZ3881@phenom.ffwll.local> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 03, 2018 at 08:08:32PM +0200, Daniel Vetter wrote: > I did not mean you should dma_map_sg/page. I just meant that using > dma_map_resource to fill only the dma address part of the sg table seems > perfectly sufficient. But that is not how the interface work, especially facing sg_dma_len. > Assuming you get an sg table that's been mapping by calling dma_map_sg was > always a bit a case of bending the abstraction to avoid typing code. The > only thing an importer ever should have done is look at the dma addresses > in that sg table, nothing else. The scatterlist is not a very good abstraction unfortunately, but it it is spread all over the kernel. And we do expect that anyone who gets passed a scatterlist can use sg_page() or sg_virt() (which calls sg_page()) on it. Your changes would break that, and will cause major trouble because of that. If you want to expose p2p memory returned from dma_map_resource in dmabuf do not use scatterlists for this please, but with a new interface that explicitly passes a virtual address, a dma address and a length and make it very clear that virt_to_page will not work on the virtual address. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 4/8] dma-buf: add peer2peer flag Date: Mon, 16 Apr 2018 05:39:37 -0700 Message-ID: <20180416123937.GA9073@infradead.org> References: <20180325110000.2238-1-christian.koenig@amd.com> <20180325110000.2238-4-christian.koenig@amd.com> <20180329065753.GD3881@phenom.ffwll.local> <8b823458-8bdc-3217-572b-509a28aae742@gmail.com> <20180403090909.GN3881@phenom.ffwll.local> <20180403170645.GB5935@redhat.com> <20180403180832.GZ3881@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20180403180832.GZ3881@phenom.ffwll.local> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Jerome Glisse , christian.koenig@amd.com, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org T24gVHVlLCBBcHIgMDMsIDIwMTggYXQgMDg6MDg6MzJQTSArMDIwMCwgRGFuaWVsIFZldHRlciB3 cm90ZToKPiBJIGRpZCBub3QgbWVhbiB5b3Ugc2hvdWxkIGRtYV9tYXBfc2cvcGFnZS4gSSBqdXN0 IG1lYW50IHRoYXQgdXNpbmcKPiBkbWFfbWFwX3Jlc291cmNlIHRvIGZpbGwgb25seSB0aGUgZG1h IGFkZHJlc3MgcGFydCBvZiB0aGUgc2cgdGFibGUgc2VlbXMKPiBwZXJmZWN0bHkgc3VmZmljaWVu dC4KCkJ1dCB0aGF0IGlzIG5vdCBob3cgdGhlIGludGVyZmFjZSB3b3JrLCBlc3BlY2lhbGx5IGZh Y2luZyBzZ19kbWFfbGVuLgoKPiBBc3N1bWluZyB5b3UgZ2V0IGFuIHNnIHRhYmxlIHRoYXQncyBi ZWVuIG1hcHBpbmcgYnkgY2FsbGluZyBkbWFfbWFwX3NnIHdhcwo+IGFsd2F5cyBhIGJpdCBhIGNh c2Ugb2YgYmVuZGluZyB0aGUgYWJzdHJhY3Rpb24gdG8gYXZvaWQgdHlwaW5nIGNvZGUuIFRoZQo+ IG9ubHkgdGhpbmcgYW4gaW1wb3J0ZXIgZXZlciBzaG91bGQgaGF2ZSBkb25lIGlzIGxvb2sgYXQg dGhlIGRtYSBhZGRyZXNzZXMKPiBpbiB0aGF0IHNnIHRhYmxlLCBub3RoaW5nIGVsc2UuCgpUaGUg c2NhdHRlcmxpc3QgaXMgbm90IGEgdmVyeSBnb29kIGFic3RyYWN0aW9uIHVuZm9ydHVuYXRlbHks IGJ1dCBpdAppdCBpcyBzcHJlYWQgYWxsIG92ZXIgdGhlIGtlcm5lbC4gIEFuZCB3ZSBkbyBleHBl Y3QgdGhhdCBhbnlvbmUgd2hvCmdldHMgcGFzc2VkIGEgc2NhdHRlcmxpc3QgY2FuIHVzZSBzZ19w YWdlKCkgb3Igc2dfdmlydCgpICh3aGljaCBjYWxscwpzZ19wYWdlKCkpIG9uIGl0LiAgWW91ciBj aGFuZ2VzIHdvdWxkIGJyZWFrIHRoYXQsIGFuZCB3aWxsIGNhdXNlIG1ham9yCnRyb3VibGUgYmVj YXVzZSBvZiB0aGF0LgoKSWYgeW91IHdhbnQgdG8gZXhwb3NlIHAycCBtZW1vcnkgcmV0dXJuZWQg ZnJvbSBkbWFfbWFwX3Jlc291cmNlIGluCmRtYWJ1ZiBkbyBub3QgdXNlIHNjYXR0ZXJsaXN0cyBm b3IgdGhpcyBwbGVhc2UsIGJ1dCB3aXRoIGEgbmV3IGludGVyZmFjZQp0aGF0IGV4cGxpY2l0bHkg cGFzc2VzIGEgdmlydHVhbCBhZGRyZXNzLCBhIGRtYSBhZGRyZXNzIGFuZCBhIGxlbmd0aAphbmQg bWFrZSBpdCB2ZXJ5IGNsZWFyIHRoYXQgdmlydF90b19wYWdlIHdpbGwgbm90IHdvcmsgb24gdGhl IHZpcnR1YWwKYWRkcmVzcy4KX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX18KZHJpLWRldmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0 b3Aub3JnCmh0dHBzOi8vbGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJp LWRldmVsCg==