From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FE89C61DF4 for ; Fri, 24 Nov 2023 09:41:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345224AbjKXJk6 (ORCPT ); Fri, 24 Nov 2023 04:40:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234988AbjKXJkx (ORCPT ); Fri, 24 Nov 2023 04:40:53 -0500 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 680B6D54 for ; Fri, 24 Nov 2023 01:40:59 -0800 (PST) Received: from localhost (cola.collaboradmins.com [195.201.22.229]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madras.collabora.co.uk (Postfix) with ESMTPSA id DD89166073A4; Fri, 24 Nov 2023 09:40:56 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1700818857; bh=LDEJxxut8mOIXIweABuj+iaxliCKCshQ6GN/RJzXq3w=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=H7NSrk1l6pFC5gIp3b4sLAuNshK1i+hDEsPF9psqr556lGfmm6VPTib3oS6SjJRzv vtTYi9Q6C59/NU5ixzekg0Y4lUnMO/aifagrBcH46kstlhMVb5SF2o5//VUL0ALir3 lUZeEUnL8WccwKfHdnbn7yRxGxkD85LjZfAL4didUTQ5MmoWMoDeX1cx/koTK2ypq7 F9VhDWI2+/HDSiXO7QQOwH6FKHpizf1n8dqKhBDvSsWAtFnwftTgUyoiARM1xoZIi6 aSvIDqVKAsehRjUqqm6P1BCqeWutZVZlWC9onUm5sRn90ZEtl4msQ7NpbQwlFHksFq zoq1XcE9f2v3A== Date: Fri, 24 Nov 2023 10:40:53 +0100 From: Boris Brezillon To: Dmitry Osipenko Cc: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Christian =?UTF-8?B?S8O2bmln?= , Qiang Yu , Steven Price , Emma Anholt , Melissa Wen , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v18 15/26] drm/panfrost: Explicitly get and put drm-shmem pages Message-ID: <20231124104053.034496fb@collabora.com> In-Reply-To: <20231123154848.034f4710@collabora.com> References: <20231029230205.93277-1-dmitry.osipenko@collabora.com> <20231029230205.93277-16-dmitry.osipenko@collabora.com> <20231123154848.034f4710@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 23 Nov 2023 15:48:48 +0100 Boris Brezillon wrote: > On Mon, 30 Oct 2023 02:01:54 +0300 > Dmitry Osipenko wrote: > > > To simplify the drm-shmem refcnt handling, we're moving away from > > the implicit get_pages() that is used by get_pages_sgt(). From now on > > drivers will have to pin pages while they use sgt. Panfrost's shrinker > > doesn't support swapping out BOs, hence pages are pinned and sgt is valid > > as long as pages' use-count > 0. > > > > Signed-off-by: Dmitry Osipenko > > --- > > drivers/gpu/drm/panfrost/panfrost_gem.c | 17 +++++++++++++++++ > > drivers/gpu/drm/panfrost/panfrost_mmu.c | 6 ++---- > > 2 files changed, 19 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c > > index 6b77d8cebcb2..bb9d43cf7c3c 100644 > > --- a/drivers/gpu/drm/panfrost/panfrost_gem.c > > +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c > > @@ -47,8 +47,13 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj) > > } > > } > > kvfree(bo->sgts); > > + > > + drm_gem_shmem_put_pages(&bo->base); > > } > > > > + if (!bo->is_heap && !obj->import_attach) > > + drm_gem_shmem_put_pages(&bo->base); > > + > > drm_gem_shmem_free(&bo->base); > > } > > > > @@ -269,6 +274,7 @@ panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags) > > { > > struct drm_gem_shmem_object *shmem; > > struct panfrost_gem_object *bo; > > + int err; > > > > /* Round up heap allocations to 2MB to keep fault handling simple */ > > if (flags & PANFROST_BO_HEAP) > > @@ -282,7 +288,18 @@ panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags) > > bo->noexec = !!(flags & PANFROST_BO_NOEXEC); > > bo->is_heap = !!(flags & PANFROST_BO_HEAP); > > > > + if (!bo->is_heap) { > > + err = drm_gem_shmem_get_pages(shmem); > > I really hate the fact we request pages here while we call > panfrost_mmu_map() in panfrost_gem_open(), because ultimately, pages > are requested for the MMU mapping. Also hate the quirk we have in shmem > to call free_pages() instead of put_pages_locked() when the BO refcount > dropped to zero, and I was hoping we could get rid of it at some point > by teaching drivers to request pages when they actually need it instead > of tying pages lifetime to the GEM object lifetime. > > Maybe what we should do instead is move the get/put_pages() in > panfrost_mmu_map/unmap() (as I suggested), but have a special mapping > panfrost_mmu_evict/restore() helpers that kill/restore the MMU mappings > without releasing/acquiring the pages ref. Okay, so I played with your branch and did what I suggested here ^. The end result is available here [1]. I also split this patch in two: - A fix for the error path in panfrost_mmu_map_fault_addr() [2] - The explicit get/put_pages() stuff with pages ref owned by the panfrost_gem_mapping object [3] [1]https://gitlab.freedesktop.org/bbrezillon/linux/-/commits/virtio-gpu-shrinker-v18 [2]https://gitlab.freedesktop.org/bbrezillon/linux/-/commit/9d499e971fdae4d6e52f8871ca27c24b2a2c43d6 [3]https://gitlab.freedesktop.org/bbrezillon/linux/-/commit/ba3de65bf1cf0ca95710e743ec85ca67ff1aa223