From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zhi Wang Subject: Re: [kraxel@redhat.com: Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations] Date: Fri, 23 Jun 2017 17:34:39 +0800 Message-ID: <594CE0AF.9070402@intel.com> References: <20170623092553.7cckmv43fmdxnbmq@zhen-hp.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20170623092553.7cckmv43fmdxnbmq@zhen-hp.sh.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Gerd Hoffmann Cc: "Wang, Zhenyu Z" , "linux-kernel@vger.kernel.org" , intel-gfx@lists.freedesktop.org, kwankhede@nvidia.com, Zhiyuan Lv , "intel-gvt-dev@lists.freedesktop.org" List-Id: intel-gfx@lists.freedesktop.org SGkgR3JlZCBhbmQgQWxleDoKICAgICBUaGFua3MgZm9yIHRoZSByZXBseSEgSXQgd291bGQgYmUg YmV0dGVyIHRoYXQga2VybmVsIG9ubHkgcHJvdmlkZXMgCmZ1bmN0aW9ucyBpbnN0ZWFkIG9mIG1h aW50YWluaW5nIHN0YXRlcyBmcm9tIG15IHBvaW50IG9mIHZpZXcuIElmIHRoZXJlIAppcyBhbnkg ZXhpc3RpbmcgYXN5bmMgbm90aWZpY2F0aW9uIGNoYW5uZWwgaW4gdmZpbyBkZXZpY2UgZmQ/IGxp a2UgCnJlcG9ydGluZyBkZXZpY2UgZXZlbnRzIGZyb20gdmZpbyB0byBRRU1VPyBJZiBzbywgSXQg d291bGQgYmUgbmljZSBpZiB3ZSAKY2FuIGV4dGVuZCB0aGF0IGNoYW5uZWwgYW5kIG5vdGlmeSB0 aGUgdXNlcnNwYWNlIGFwcGxpY2F0aW9uIHRoYXQgZ3Vlc3QgCmZyYW1lYnVmZmVyIGNoYW5nZWQg dmlhIHRoYXQgY2hhbm5lbC4gU28gdXNlcnNwYWNlIGFwcGxpY2F0aW9uIGV2ZW4gCmRvZXNuJ3Qg bmVlZCB0byBjYWxsIHRoZSBpb2N0bCBwZXJpb2RpY2FsbHkuIDopIElmIFZNIHJ1bnMgYSAKc2lu Z2xlLWJ1ZmZlcmVkIGFwcGxpY2F0aW9uLgoKVGhhbmtzLApaaGkuCgpPbiBGcmksIDIwMTctMDYt MjMgYXQgMTU6NDkgKzA4MDAsIFpoaSBXYW5nIHdyb3RlOgo+PiBIaToKPj4gICAgICAgVGhhbmtz IGZvciB0aGUgZGlzY3Vzc2lvbnMhIElmIHRoZSB1c2Vyc3BhY2UgYXBwbGljYXRpb24gaGFzCj4+ IGFscmVhZHkgbWFpbnRhaW5lZCBhIExSVSBsaXN0LCBpdCBsb29rcyBsaWtlIHdlIGRvbid0IG5l ZWQKPj4gZ2VuZXJhdGlvbgo+PiBhbnltb3JlLAo+IGdlbmVyYXRpb24gaXNuJ3QgcmVxdWlyZWQs IHRoaW5ncyBhcmUgd29ya2luZyBqdXN0IGZpbmUgd2l0aG91dCB0aGF0Lgo+IEl0IGlzIGp1c3Qg YSBzbWFsbCBvcHRpbWl6YXRpb24sIHVzZXJzcGFjZSBjYW4gc2tpcCB0aGUgTFJVIGxvb2t1cAo+ IGFsdG9nZXRoZXIgaWYgdGhlIGdlbmVyYXRpb24gZGlkbid0IGNoYW5nZS4KPgo+IEJ1dCBvZiBj b3VzZSB0aGF0IG9ubHkgcGF5cyBvZmYgaWYgdGhlIGtlcm5lbCBkb2Vzbid0IGhhcyB0byBwdXQg bXVjaAo+IGVmZm9ydCBpbnRvIG1haW50YWluaW5nIHRoZSBnZW5lcmF0aW9uIGlkLiAgU29tZXRo aW5nIHNpbXBsZSBsaWtlCj4gaW5jcmVhc2luZyBpdCBlYWNoIHRpbWUgdGhlIGd1ZXN0IHdyaXRl cyBhIHJlZ2lzdGVyIHdoaWNoIGFmZmVjdHMKPiBwbGFuZV9pbmZvLgo+Cj4gSWYgeW91IHRoaW5r IGl0IGRvZXNuJ3QgbWFrZSBzZW5zZSBmcm9tIHRoZSBkcml2ZXIgcG9pbnQgb2YgdmlldyB3ZSBj YW4KPiBkcm9wIHRoZSBnZW5lcmF0aW9uLgo+Cj4gY2hlZXJzLAo+ICAgIEdlcmQKX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KSW50ZWwtZ2Z4IG1haWxpbmcg bGlzdApJbnRlbC1nZnhAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlzdHMuZnJlZWRl c2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vaW50ZWwtZ2Z4Cg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754651AbdFWJrW (ORCPT ); Fri, 23 Jun 2017 05:47:22 -0400 Received: from mga05.intel.com ([192.55.52.43]:60659 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754457AbdFWJrV (ORCPT ); Fri, 23 Jun 2017 05:47:21 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,377,1493708400"; d="scan'208";a="117961792" Message-ID: <594CE0AF.9070402@intel.com> Date: Fri, 23 Jun 2017 17:34:39 +0800 From: Zhi Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Gerd Hoffmann CC: Alex Williamson , "Wang, Zhenyu Z" , intel-gfx@lists.freedesktop.org, "linux-kernel@vger.kernel.org" , "Zhang, Tina" , kwankhede@nvidia.com, Zhiyuan Lv , "intel-gvt-dev@lists.freedesktop.org" Subject: Re: [kraxel@redhat.com: Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations] References: <20170623092553.7cckmv43fmdxnbmq@zhen-hp.sh.intel.com> In-Reply-To: <20170623092553.7cckmv43fmdxnbmq@zhen-hp.sh.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gred and Alex: Thanks for the reply! It would be better that kernel only provides functions instead of maintaining states from my point of view. If there is any existing async notification channel in vfio device fd? like reporting device events from vfio to QEMU? If so, It would be nice if we can extend that channel and notify the userspace application that guest framebuffer changed via that channel. So userspace application even doesn't need to call the ioctl periodically. :) If VM runs a single-buffered application. Thanks, Zhi. On Fri, 2017-06-23 at 15:49 +0800, Zhi Wang wrote: >> Hi: >> Thanks for the discussions! If the userspace application has >> already maintained a LRU list, it looks like we don't need >> generation >> anymore, > generation isn't required, things are working just fine without that. > It is just a small optimization, userspace can skip the LRU lookup > altogether if the generation didn't change. > > But of couse that only pays off if the kernel doesn't has to put much > effort into maintaining the generation id. Something simple like > increasing it each time the guest writes a register which affects > plane_info. > > If you think it doesn't make sense from the driver point of view we can > drop the generation. > > cheers, > Gerd