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 37B2ECCFA1E for ; Tue, 11 Nov 2025 16:45:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0074310E626; Tue, 11 Nov 2025 16:45:27 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="dvKio0UA"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.11]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0F2C210E628; Tue, 11 Nov 2025 16:45:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1762879525; x=1794415525; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=bD7vg0Imwvw+C2f4GGwhVmom6OFe1El4o2bBLXiS8nM=; b=dvKio0UAFLkeYS5FFsneh5ZI5BVvBvP2qrhIXVR5xmaImCCsUypdfO5q GN2A8TOu6+BnxXbxuQBA+BTthIvOQHWlXXICMf8168GdkTfDFiGqSytuI dhbTHd4K1UO4OZPP9QZobrewroaS78iGk2+L/qG/dUBRcAyO7w2Yy4EKU u0PXT8EBSp8C/ZqwJJSrpGePtXgCjn+pM3aFEW5IobMnaTX5+5oAc2yDm 9YLBmizV16+zOax/5mmlYtKQ+TaQvaWg6MYnrXlNK6V9M213x+YbmGPT+ mIcqiT0lH+Bo8hz9iPcIuSKEuwAYt0cFOOmgd9COQ2PvWyuq7jgbtkNJB w==; X-CSE-ConnectionGUID: WYddKrt/Rri2QPkDr67LQw== X-CSE-MsgGUID: NNywEKbDQmqMZMZc5fZEaw== X-IronPort-AV: E=McAfee;i="6800,10657,11610"; a="75244801" X-IronPort-AV: E=Sophos;i="6.19,297,1754982000"; d="scan'208";a="75244801" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2025 08:45:25 -0800 X-CSE-ConnectionGUID: tlKP5hqQSDKPQYzMMs1toQ== X-CSE-MsgGUID: lTrMO2/xTe+aZ2GM8OMSNw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,297,1754982000"; d="scan'208";a="188647005" Received: from rvuia-mobl.ger.corp.intel.com (HELO fedora) ([10.245.244.91]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2025 08:45:22 -0800 From: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= To: intel-xe@lists.freedesktop.org Cc: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Matthew Brost , dri-devel@lists.freedesktop.org, himal.prasad.ghimiray@intel.com, apopple@nvidia.com, airlied@gmail.com, Simona Vetter , felix.kuehling@amd.com, =?UTF-8?q?Christian=20K=C3=B6nig?= , dakr@kernel.org, "Mrozek, Michal" , Joonas Lahtinen Subject: [PATCH v2 17/17] drm/xe/svm: Document how xe keeps drm_pagemap references Date: Tue, 11 Nov 2025 17:44:07 +0100 Message-ID: <20251111164408.113070-18-thomas.hellstrom@linux.intel.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251111164408.113070-1-thomas.hellstrom@linux.intel.com> References: <20251111164408.113070-1-thomas.hellstrom@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" As an aid to understanding the lifetime of the drm_pagemaps used by the xe driver, document how the xe driver keeps the drm_pagemap references. Suggested-by: Matthew Brost Signed-off-by: Thomas Hellström --- drivers/gpu/drm/xe/xe_svm.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c index 56bb3896b89a..c1d6eb2f97d1 100644 --- a/drivers/gpu/drm/xe/xe_svm.c +++ b/drivers/gpu/drm/xe/xe_svm.c @@ -28,6 +28,28 @@ #define XE_PEER_PAGEMAP ((void *)0ul) #define XE_PEER_VM ((void *)1ul) +/** + * DOC: drm_pagemap reference-counting in xe: + * + * In addition to the drm_pagemap internal reference counting by + * its zone device data, the xe driver holds the following + * long-time references: + * + * - struct xe_pagemap: + * The xe_pagemap struct derives from struct drm_pagemap and + * uses its reference count. + * - SVM-enabled VMs: + * SVM-enabled VMs look up and keeps a reference to all + * xe_pagemaps on the same device. + * - VMAs: + * vmas keep a reference on the drm_pagemap indicated by a gpu_madvise() + * call. + * + * In addition, all drm_pagemap or xe_pagemap pointers where lifetime cannot + * be guaranteed by a vma reference under the vm lock should keep a reference. + * That includes the range->pages.dpagemap pointer. + */ + static int xe_svm_get_pagemaps(struct xe_vm *vm); void *xe_svm_private_page_owner(struct xe_vm *vm, bool force_smem) -- 2.51.1