From patchwork Fri Nov 22 20:57:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Niranjana Vishwanathapura X-Patchwork-Id: 11258419 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E5C24109A for ; Fri, 22 Nov 2019 21:09:14 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id CDEF620708 for ; Fri, 22 Nov 2019 21:09:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CDEF620708 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0A0316F578; Fri, 22 Nov 2019 21:09:02 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id AAC826F574; Fri, 22 Nov 2019 21:09:00 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Nov 2019 13:08:59 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,231,1571727600"; d="scan'208";a="205575837" Received: from nvishwa1-desk.sc.intel.com ([10.3.160.185]) by fmsmga007.fm.intel.com with ESMTP; 22 Nov 2019 13:08:59 -0800 From: Niranjana Vishwanathapura To: intel-gfx@lists.freedesktop.org Subject: [RFC 01/13] drm/i915/svm: Add SVM documentation Date: Fri, 22 Nov 2019 12:57:22 -0800 Message-Id: <20191122205734.15925-2-niranjana.vishwanathapura@intel.com> X-Mailer: git-send-email 2.21.0.rc0.32.g243a4c7e27 In-Reply-To: <20191122205734.15925-1-niranjana.vishwanathapura@intel.com> References: <20191122205734.15925-1-niranjana.vishwanathapura@intel.com> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: sanjay.k.kumar@intel.com, sudeep.dutt@intel.com, dri-devel@lists.freedesktop.org, dave.hansen@intel.com, jglisse@redhat.com, jon.bloomfield@intel.com, daniel.vetter@intel.com, dan.j.williams@intel.com, ira.weiny@intel.com, jgg@mellanox.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Add Shared Virtual Memory (SVM) support information. Cc: Joonas Lahtinen Cc: Jon Bloomfield Cc: Daniel Vetter Cc: Sudeep Dutt Signed-off-by: Niranjana Vishwanathapura --- Documentation/gpu/i915.rst | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst index d0947c5c4ab8..592fc26d2ca0 100644 --- a/Documentation/gpu/i915.rst +++ b/Documentation/gpu/i915.rst @@ -415,6 +415,35 @@ Object Tiling IOCTLs .. kernel-doc:: drivers/gpu/drm/i915/gem/i915_gem_tiling.c :doc: buffer object tiling +Shared Virtual Memory (SVM) +--------------------------- + +Shared Virtual Memory (SVM) allows the programmer to use a single virtual +address space which will be shared between threads executing on CPUs and GPUs. +It abstracts away from the user the location of the backing memory, and hence +simplifies the user programming model. +SVM supports two types of virtual memory allocation methods. +Runtime allocator requires the driver to provide memory allocation and +management interface, like buffer object (BO) interface. +Whereas system allocator makes use of default OS memory allocation and +management support like malloc(). + +Linux kernel has a Heterogeneous Memory Management (HMM) framework to +Support SVM system allocator. HMM’s address space mirroring support allows +sharing of the address space by duplicating sections of CPU page tables in the +device page tables. This enables both CPU and GPU access a physical memory +location using the same virtual address. Linux kernel also provides the ability +to plugin device memory with the system (as a special ZONE_DEVICE type) and +allocates struct page for each device memory page. It also provides a mechanism +to migrate pages from host to device memory and vice versa. +More information on HMM can be found here. +https://www.kernel.org/doc/Documentation/vm/hmm.rst + +i915 supports both SVM system and runtime allocator. As PCIe is a non-coherent +bus, it plugs in device memory as DEVICE_PRIVATE and no memory access across +PCIe link is allowed. Any such access will trigger migration of the page/s +or BOs before the memory is accessed. + Microcontrollers ================