From patchwork Fri Feb 18 11:22:42 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Matthew Auld X-Patchwork-Id: 12751369 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 91BBFC433F5 for ; Fri, 18 Feb 2022 11:25:41 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4D99B10EBC8; Fri, 18 Feb 2022 11:25:36 +0000 (UTC) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2233910EB6D; Fri, 18 Feb 2022 11:25:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1645183534; x=1676719534; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Kh3FWTS4xZseG7yZOg8TEFsI+jqdY/b5oguxmUagu+s=; b=bHDVMUy4PTYpRNXiZAm1cbct2p4pSygR+NrtAV89+RofE3Oyg/NfaQT7 LB9Z+3o+6u4fvFwrkC7npHVSB/OMIdY6ZbK2ygSPVloQin6FZD2t6zDA0 p8bZ6e3hbwT/p/Al9qNu/BcwhGWKlRsBD0rtLd4wd42XfN5k7yuLWg29+ M1WBeWB74IZnAznTIhEKptz8KQl3+fMJ+M3H1K0iqzXuaBmF5+08AMBoA NjLfO+sEJNrpaop4sS5PwFlLG2QNS0ATvO3sriugcftRVCxZvsrZ+Kt5y DR/mTwVd2namBCA5QCjzKn56Gvhkaq3ZskI/xUQYzgupNh6k32J8nUAn8 Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10261"; a="238512859" X-IronPort-AV: E=Sophos;i="5.88,378,1635231600"; d="scan'208";a="238512859" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2022 03:25:33 -0800 X-IronPort-AV: E=Sophos;i="5.88,378,1635231600"; d="scan'208";a="705344784" Received: from jawiblin-mobl.ger.corp.intel.com (HELO mwauld-desk1.intel.com) ([10.252.23.195]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2022 03:25:31 -0800 From: Matthew Auld To: intel-gfx@lists.freedesktop.org Subject: [PATCH 2/2] drm/doc: add rfc section for small BAR uapi Date: Fri, 18 Feb 2022 11:22:42 +0000 Message-Id: <20220218112242.2117968-3-matthew.auld@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220218112242.2117968-1-matthew.auld@intel.com> References: <20220218112242.2117968-1-matthew.auld@intel.com> MIME-Version: 1.0 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: , Cc: =?utf-8?q?Thomas_Hellstr=C3=B6m?= , Jordan Justen , dri-devel@lists.freedesktop.org, Kenneth Graunke , Jon Bloomfield , Daniel Vetter , mesa-dev@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Add an entry for the new uapi needed for small BAR on DG2+. Signed-off-by: Matthew Auld Cc: Thomas Hellström Cc: Jon Bloomfield Cc: Daniel Vetter Cc: Jordan Justen Cc: Kenneth Graunke Cc: mesa-dev@lists.freedesktop.org Acked-by: Thomas Hellström --- Documentation/gpu/rfc/i915_small_bar.h | 153 +++++++++++++++++++++++ Documentation/gpu/rfc/i915_small_bar.rst | 40 ++++++ Documentation/gpu/rfc/index.rst | 4 + 3 files changed, 197 insertions(+) create mode 100644 Documentation/gpu/rfc/i915_small_bar.h create mode 100644 Documentation/gpu/rfc/i915_small_bar.rst diff --git a/Documentation/gpu/rfc/i915_small_bar.h b/Documentation/gpu/rfc/i915_small_bar.h new file mode 100644 index 000000000000..fa65835fd608 --- /dev/null +++ b/Documentation/gpu/rfc/i915_small_bar.h @@ -0,0 +1,153 @@ +/** + * struct __drm_i915_gem_create_ext - Existing gem_create behaviour, with added + * extension support using struct i915_user_extension. + * + * Note that in the future we want to have our buffer flags here, at least for + * the stuff that is immutable. Previously we would have two ioctls, one to + * create the object with gem_create, and another to apply various parameters, + * however this creates some ambiguity for the params which are considered + * immutable. Also in general we're phasing out the various SET/GET ioctls. + */ +struct __drm_i915_gem_create_ext { + /** + * @size: Requested size for the object. + * + * The (page-aligned) allocated size for the object will be returned. + * + * Note that for some devices we have might have further minimum + * page-size restrictions(larger than 4K), like for device local-memory. + * However in general the final size here should always reflect any + * rounding up, if for example using the I915_GEM_CREATE_EXT_MEMORY_REGIONS + * extension to place the object in device local-memory. + */ + __u64 size; + /** + * @handle: Returned handle for the object. + * + * Object handles are nonzero. + */ + __u32 handle; + /** + * @flags: Optional flags. + * + * Supported values: + * + * I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS - Signal to the kernel that + * the object will need to be accessed via the CPU. + * + * Only valid when placing objects in I915_MEMORY_CLASS_DEVICE, and + * only strictly required on platforms where only some of the device + * memory is directly visible or mappable through the CPU, like on DG2+. + * + * One of the placements MUST also be I915_MEMORY_CLASS_SYSTEM, to + * ensure we can always spill the allocation to system memory, if we + * can't place the object in the mappable part of + * I915_MEMORY_CLASS_DEVICE. + * + * Note that buffers that need to be captured with EXEC_OBJECT_CAPTURE, + * will need to enable this hint, if the object can also be placed in + * I915_MEMORY_CLASS_DEVICE, starting from DG2+. The execbuf call will + * throw an error otherwise. This also means that such objects will need + * I915_MEMORY_CLASS_SYSTEM set as a possible placement. + * + * Without this hint, the kernel will assume that non-mappable + * I915_MEMORY_CLASS_DEVICE is preferred for this object. Note that the + * kernel can still migrate the object to the mappable part, as a last + * resort, if userspace ever CPU faults this object, but this might be + * expensive, and so ideally should be avoided. + */ +#define I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS (1 << 0) + __u32 flags; + /** + * @extensions: The chain of extensions to apply to this object. + * + * This will be useful in the future when we need to support several + * different extensions, and we need to apply more than one when + * creating the object. See struct i915_user_extension. + * + * If we don't supply any extensions then we get the same old gem_create + * behaviour. + * + * For I915_GEM_CREATE_EXT_MEMORY_REGIONS usage see + * struct drm_i915_gem_create_ext_memory_regions. + * + * For I915_GEM_CREATE_EXT_PROTECTED_CONTENT usage see + * struct drm_i915_gem_create_ext_protected_content. + */ +#define I915_GEM_CREATE_EXT_MEMORY_REGIONS 0 +#define I915_GEM_CREATE_EXT_PROTECTED_CONTENT 1 + __u64 extensions; +}; + +#define DRM_I915_QUERY_VMA_INFO 5 + +/** + * struct __drm_i915_query_vma_info + * + * Given a vm and GTT address, lookup the corresponding vma, returning its set + * of attributes. + * + * .. code-block:: C + * + * struct drm_i915_query_vma_info info = {}; + * struct drm_i915_query_item item = { + * .data_ptr = (uintptr_t)&info, + * .query_id = DRM_I915_QUERY_VMA_INFO, + * }; + * struct drm_i915_query query = { + * .num_items = 1, + * .items_ptr = (uintptr_t)&item, + * }; + * int err; + * + * // Unlike some other types of queries, there is no need to first query + * // the size of the data_ptr blob here, since we already know ahead of + * // time how big this needs to be. + * item.length = sizeof(info); + * + * // Next we fill in the vm_id and ppGTT address of the vma we wish + * // to query, before then firing off the query. + * info.vm_id = vm_id; + * info.offset = gtt_address; + * err = ioctl(fd, DRM_IOCTL_I915_QUERY, &query); + * if (err || item.length < 0) ... + * + * // If all went well we can now inspect the returned attributes. + * if (info.attributes & DRM_I915_QUERY_VMA_INFO_CPU_VISIBLE) ... + */ +struct __drm_i915_query_vma_info { + /** + * @vm_id: The given vm id that contains the vma. The id is the value + * returned by the DRM_I915_GEM_VM_CREATE. See struct + * drm_i915_gem_vm_control.vm_id. + */ + __u32 vm_id; + /** @pad: MBZ. */ + __u32 pad; + /** + * @offset: The corresponding ppGTT address of the vma which the kernel + * will use to perform the lookup. + */ + __u64 offset; + /** + * @attributes: The returned attributes for the given vma. + * + * Possible values: + * + * DRM_I915_QUERY_VMA_INFO_CPU_VISIBLE - Set if the pages backing the + * vma are currently CPU accessible. If this is not set then the vma is + * currently backed by I915_MEMORY_CLASS_DEVICE memory, which the CPU + * cannot directly access(this is only possible on discrete devices with + * a small BAR). Attempting to MMAP and fault such an object will + * require the kernel first synchronising any GPU work tied to the + * object, before then migrating the pages, either to the CPU accessible + * part of I915_MEMORY_CLASS_DEVICE, or I915_MEMORY_CLASS_SYSTEM, if the + * placements permit it. See I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS. + * + * Note that this is inherently racy. + */ +#define DRM_I915_QUERY_VMA_INFO_CPU_VISIBLE (1<<0) + __u64 attributes; + /** @rsvd: MBZ */ + __u32 rsvd[4]; +}; diff --git a/Documentation/gpu/rfc/i915_small_bar.rst b/Documentation/gpu/rfc/i915_small_bar.rst new file mode 100644 index 000000000000..fea92d3d69ab --- /dev/null +++ b/Documentation/gpu/rfc/i915_small_bar.rst @@ -0,0 +1,40 @@ +========================== +I915 Small BAR RFC Section +========================== +Starting from DG2 we will have resizable BAR support for device local-memory, +but in some cases the final BAR size might still be smaller than the total +local-memory size. In such cases only part of local-memory will be CPU +accessible, while the remainder is only accessible via the GPU. + +I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS flag +---------------------------------------------- +New gem_create_ext flag to tell the kernel that a BO will require CPU access. +The becomes important when placing an object in LMEM, where underneath the +device has a small BAR, meaning only part of it is CPU accessible. Without this +flag the kernel will assume that CPU access is not required, and prioritize +using the non-CPU visible portion of LMEM(if present on the device). + +Related to this, we now also reject any objects marked with +EXEC_OBJECT_CAPTURE, which are also not tagged with NEEDS_CPU_ACCESS. This only +impacts DG2+. + +XXX: One open here is whether we should extend the memory region query to return +the CPU visible size of the region. For now the IGTs just use debugfs to query +the size. However, if userspace sees a real need for this then extending the +region query would be a lot nicer. + +.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h + :functions: __drm_i915_gem_create_ext + +DRM_I915_QUERY_VMA_INFO query +----------------------------- +Query the attributes of some vma. Given a vm and GTT offset, find the +respective vma, and return its set of attrubutes. For now we only support +DRM_I915_QUERY_VMA_INFO_CPU_VISIBLE, which is set if the object/vma is +currently placed in memory that is accessible by the CPU. This should always be +set on devices where the CPU visible size of LMEM matches the probed size. If +this is not set then CPU faulting the object will first require migrating the +pages. + +.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h + :functions: __drm_i915_query_vma_info diff --git a/Documentation/gpu/rfc/index.rst b/Documentation/gpu/rfc/index.rst index 018a8bf317a6..5b8495bdc1fd 100644 --- a/Documentation/gpu/rfc/index.rst +++ b/Documentation/gpu/rfc/index.rst @@ -19,3 +19,7 @@ host such documentation: .. toctree:: i915_scheduler.rst + +.. toctree:: + + i915_small_bar.rst