From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerd Hoffmann Subject: Re: [PATCH v6 6/6] drm/i915/gvt: Adding interface so user space can get the dma-buf Date: Fri, 02 Jun 2017 17:23:58 +0200 Message-ID: <1496417038.16895.7.camel@redhat.com> References: <1495874332-2851-1-git-send-email-xiaoguang.chen@intel.com> <1495874332-2851-7-git-send-email-xiaoguang.chen@intel.com> <20170601120820.3358f7dd@w520.home> <20170601213459.461ecf36@w520.home> <20170602085831.41454a1f@t450s.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20170602085831.41454a1f@t450s.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Alex Williamson , "Chen, Xiaoguang" Cc: "intel-gfx@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "Lv, Zhiyuan" , "intel-gvt-dev@lists.freedesktop.org" List-Id: intel-gfx@lists.freedesktop.org ICBIaSwKCj4gPiBXaGVuIGk5MTUncyBkbWEtYnVmJ3MgcmVsZWFzZSgpIGNhbGxiYWNrIGlzIGNh bGxlZCBpdCB3aWxsIHRyeSB0bwo+ID4gZnJlZSB0aGUgZ2VtIG9iamVjdCBhc3NvY2lhdGVkIHdp dGggdGhlIGRtYS1idWYgaWYgaXRzIHJlZiBjb3VudCBpcwo+ID4gMC4gQnV0IGluIG91ciBjYXNl IHRoZSByZWYgY291bnQgaXMgMSBzbyBubyBmcmVlIGNhbGxiYWNrIGlzIGNhbGxlZAo+ID4gc28g d2UgY2FuIG5vdCByZWxlYXNlIGFsbG9jYXRpb25zIHRoZXJlLgoKV2h5IHRoZSByZWYgY291bnQg aXMgb25lPyAgV2hvIGhvbGRzIGEgcmVmZXJlbmNlIGFuZCB3aHk/Ck1heWJlIGl0IHNob3VsZCBi ZSB0aGUgb3RoZXIgd2F5IGFyb3VuZCwgaS5lLiB0aGUgZG1hYnVmIGhvbGRzIGEKcmVmZXJlbmNl IG9uIHRoZSB2Z3B1IGluc3RhbmNlIGJhY2tpbmcgaXQsIGkuZS4geW91IGNhbid0IGRlbGV0ZSB0 aGUKdmdwdSB3aGlsZSBkbWEtYnVmcyBleGlzdD8KCj4gV2UgY2Fubm90IHNpbXBseSBzYXkgdGhh dCB0aGUgdXNlciBpc24ndCBhbGxvd2VkIHRvIHJlbGVhc2UgdGhlbSBpbgo+IHRoYXQgb3JkZXIu CgpZZXAsIG5vdCBnb2luZyB0byBmbHkuICBDYW4gaGFwcGVuIGV2ZW4gdW5pbnRlbnRpb25hbGx5 IGJlY2F1c2Ugd2UgY2FuCnBhc3MgYXJvdW5kIGRtYWJ1ZnMgdG8gb3RoZXIgcHJvY2Vzc2VzLiAg RXhhbXBsZTogcWVtdSBwYXNzZXMgZG1hYnVmIHRvCnNwaWNlLWNsaWVudCwgdGhlbiBxZW11IGNy YXNoZXMuICBtZ210IGZkIGlzIGNsb3NlZCBiZWZvcmUgZG1hYnVmIGZkCnRoZW4uICBUaGUga2Vy bmVsIG11c3QgYmUgYWJsZSB0byBoYW5kbGUgdGhhdC4KCmNoZWVycywKICBHZXJkCl9fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkludGVsLWdmeCBtYWlsaW5n IGxpc3QKSW50ZWwtZ2Z4QGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3RzLmZyZWVk ZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2ludGVsLWdmeAo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751258AbdFBPYE convert rfc822-to-8bit (ORCPT ); Fri, 2 Jun 2017 11:24:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59012 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbdFBPYD (ORCPT ); Fri, 2 Jun 2017 11:24:03 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 7AE3E80F95 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=kraxel@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 7AE3E80F95 Message-ID: <1496417038.16895.7.camel@redhat.com> Subject: Re: [PATCH v6 6/6] drm/i915/gvt: Adding interface so user space can get the dma-buf From: Gerd Hoffmann To: Alex Williamson , "Chen, Xiaoguang" Cc: "chris@chris-wilson.co.uk" , "intel-gfx@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "zhenyuw@linux.intel.com" , "Lv, Zhiyuan" , "intel-gvt-dev@lists.freedesktop.org" , "Wang, Zhi A" , "Tian, Kevin" Date: Fri, 02 Jun 2017 17:23:58 +0200 In-Reply-To: <20170602085831.41454a1f@t450s.home> References: <1495874332-2851-1-git-send-email-xiaoguang.chen@intel.com> <1495874332-2851-7-git-send-email-xiaoguang.chen@intel.com> <20170601120820.3358f7dd@w520.home> <20170601213459.461ecf36@w520.home> <20170602085831.41454a1f@t450s.home> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Mime-Version: 1.0 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 02 Jun 2017 15:24:03 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, > > When i915's dma-buf's release() callback is called it will try to > > free the gem object associated with the dma-buf if its ref count is > > 0. But in our case the ref count is 1 so no free callback is called > > so we can not release allocations there. Why the ref count is one? Who holds a reference and why? Maybe it should be the other way around, i.e. the dmabuf holds a reference on the vgpu instance backing it, i.e. you can't delete the vgpu while dma-bufs exist? > We cannot simply say that the user isn't allowed to release them in > that order. Yep, not going to fly. Can happen even unintentionally because we can pass around dmabufs to other processes. Example: qemu passes dmabuf to spice-client, then qemu crashes. mgmt fd is closed before dmabuf fd then. The kernel must be able to handle that. cheers, Gerd