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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C10EDCD5BB1 for ; Tue, 26 May 2026 21:29:37 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2E9B910E5F8; Tue, 26 May 2026 21:29:37 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="idXhLw6g"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6BA8410E648 for ; Tue, 26 May 2026 21:29:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1779830971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9iRHxmN/dnU79hS18x4XdzAf0Ghs0AIzOreSmFvd9Ao=; b=idXhLw6gVoCrJrXKni4WvwAIABVjWyla9iPVA410ClAI+YvTmYLwSjN8uBMquBzBWsQDiF yMkHkOs5zZRD5i4T6k3KI+QaGxKGdtBlqbXN/J62J+N8rPEJGRLXL/gGXjOLN/tMvt7oPD YbUf2IvKJjKQDl/OHeX1esBTWZLA/Os= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-671-b078CjYyMn6pwNS1BSK2Ow-1; Tue, 26 May 2026 17:29:27 -0400 X-MC-Unique: b078CjYyMn6pwNS1BSK2Ow-1 X-Mimecast-MFC-AGG-ID: b078CjYyMn6pwNS1BSK2Ow_1779830964 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B7C721956080; Tue, 26 May 2026 21:29:23 +0000 (UTC) Received: from GoldenWind.lan (unknown [10.22.64.238]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 6ECCB30001BB; Tue, 26 May 2026 21:29:20 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org, nouveau@lists.freedesktop.org Cc: Alexandre Courbot , Gary Guo , =?UTF-8?q?Christian=20K=C3=B6nig?= , driver-core@lists.linux.dev, Miguel Ojeda , Maarten Lankhorst , Alice Ryhl , Simona Vetter , linux-kernel@vger.kernel.org, Sumit Semwal , linux-media@vger.kernel.org, "Rafael J . Wysocki" , Thomas Zimmermann , Maxime Ripard , David Airlie , Benno Lossin , linaro-mm-sig@lists.linaro.org, Danilo Krummrich , Mukesh Kumar Chaurasiya , Asahi Lina , Daniel Almeida , Lyude Paul , Greg Kroah-Hartman Subject: [PATCH v14 4/6] drm/gem/shmem: Introduce __drm_gem_shmem_free_sgt_locked() Date: Tue, 26 May 2026 17:28:55 -0400 Message-ID: <20260526212857.1158294-5-lyude@redhat.com> In-Reply-To: <20260526212857.1158294-1-lyude@redhat.com> References: <20260526212857.1158294-1-lyude@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: A3R-5L2TkJLGanKoEQxH5aqLRNZFA5JTXQKptQLxE8Y_1779830964 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" One of the complications of trying to use the shmem helpers to create a scatterlist for shmem objects is that we need to be able to provide a guarantee that the driver cannot be unbound for the lifetime of the scatterlist. The easiest way of handling this seems to be just hooking up an unmap operation to devres the first time we create a scatterlist, which allows us to still take advantage of gem shmem facilities without breaking that guarantee. To allow for this, we extract __drm_gem_shmem_free_sgt_locked() - which allows a caller (e.g. the rust bindings) to manually unmap the sgt for a gem object as needed. Signed-off-by: Lyude Paul Reviewed-by: Alexandre Courbot --- V10: * Fix incorrect function name in documentation for __drm_gem_shmem_release_sgt_locked() drivers/gpu/drm/drm_gem_shmem_helper.c | 32 +++++++++++++++++++++----- include/drm/drm_gem_shmem_helper.h | 1 + 2 files changed, 27 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 545933c7f7121..c989459eb2159 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -158,6 +158,30 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t } EXPORT_SYMBOL_GPL(drm_gem_shmem_create); +/** + * __drm_gem_shmem_release_sgt_locked - Unpin and DMA unmap pages, and release the + * cached scatter/gather table for an shmem GEM object. + * @shmem: shmem GEM object + * + * If the passed shmem object has an active scatter/gather table for driver + * usage, this function will unmap it and release the memory associated with it. + * It is the responsibility of the caller to ensure it holds the dma_resv_lock + * for this object. + * + * Drivers should not need to call this function themselves, it is mainly + * intended for usage in the Rust shmem bindings. + */ +void __drm_gem_shmem_free_sgt_locked(struct drm_gem_shmem_object *shmem) +{ + dma_resv_assert_held(shmem->base.resv); + + dma_unmap_sgtable(shmem->base.dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0); + sg_free_table(shmem->sgt); + kfree(shmem->sgt); + shmem->sgt = NULL; +} +EXPORT_SYMBOL_GPL(__drm_gem_shmem_free_sgt_locked); + /** * drm_gem_shmem_release - Release resources associated with a shmem GEM object. * @shmem: shmem GEM object @@ -176,12 +200,8 @@ void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem) drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count)); - if (shmem->sgt) { - dma_unmap_sgtable(obj->dev->dev, shmem->sgt, - DMA_BIDIRECTIONAL, 0); - sg_free_table(shmem->sgt); - kfree(shmem->sgt); - } + if (shmem->sgt) + __drm_gem_shmem_free_sgt_locked(shmem); if (shmem->pages) drm_gem_shmem_put_pages_locked(shmem); diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index 5ccdae21b94a9..b2c23af628e1a 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -111,6 +111,7 @@ int drm_gem_shmem_init(struct drm_device *dev, struct drm_gem_shmem_object *shme struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size); void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem); void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem); +void __drm_gem_shmem_free_sgt_locked(struct drm_gem_shmem_object *shmem); void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem); int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem); -- 2.54.0