From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx194.postini.com [74.125.245.194]) by kanga.kvack.org (Postfix) with SMTP id 3FA598D0002 for ; Fri, 11 May 2012 19:39:50 -0400 (EDT) Received: by yenm7 with SMTP id m7so4615118yen.14 for ; Fri, 11 May 2012 16:39:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1335188594-17454-4-git-send-email-inki.dae@samsung.com> <1336544259-17222-1-git-send-email-inki.dae@samsung.com> <1336544259-17222-3-git-send-email-inki.dae@samsung.com> <001501cd2e4d$c7dbc240$579346c0$%dae@samsung.com> <4FAB4AD8.2010200@kernel.org> <002401cd2e7a$1e8b0ed0$5ba12c70$%dae@samsung.com> <4FAB68CF.8000404@kernel.org> <4FAB782C.306@kernel.org> <003301cd2e89$13f78c00$3be6a400$%dae@samsung.com> <4FAC0091.7070606@gmail.com> <4FAC623E.7090209@kernel.org> <4FAC7EBA.1080708@gmail.com> <4FAD829E.2030707@gmail.com> <4FAD99E1.4090600@gmail.com> From: KOSAKI Motohiro Date: Fri, 11 May 2012 19:39:29 -0400 Message-ID: Subject: Re: [PATCH 2/2 v3] drm/exynos: added userptr feature. Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Glisse Cc: Minchan Kim , Inki Dae , InKi Dae , airlied@linux.ie, dri-devel@lists.freedesktop.org, kyungmin.park@samsung.com, sw0312.kim@samsung.com, linux-mm@kvack.org On Fri, May 11, 2012 at 7:29 PM, Jerome Glisse wrote: > On Fri, May 11, 2012 at 6:59 PM, KOSAKI Motohiro > wrote: >>> My point is this ioctl will be restricted to one user (Xserver if i >>> understand) and only this user, there is no fork in it so no need to >>> worry about fork, just setting the vma as locked will be enough. >>> >>> But i don't want people reading this driver suddenly think that what >>> it's doing is ok, it's not, it's hack and can never make to work >>> properly on a general case, that's why it needs a big comment stating, >>> stressing that. I just wanted to make sure Inki and Kyungmin >>> understood that this kind of ioctl should be restricted to carefully >>> selected user and that there is no way to make it general or reliable >>> outside that. >> >> >> first off, I'm not drm guy and then I don't intend to insist you. but if >> application don't use fork, get_user_pages() has no downside. I guess we >> don't need VM_LOCKED hack. >> >> but again, up to drm folks. > > You need the VM_LOCKED hack to mare sure that the xorg vma still point > to the same page, afaict with get_user_pages pages can be migrated out > of the anonymous vma so the vma might point to new page, while old > page are still in use by the gpu and not recycle until their refcount > drop to 0. afaik, get_user_pages() prevent page migration. (see migrate_page_move_mapping). but mlock doesn't. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org