From patchwork Wed Apr 20 17:13:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Matthew Auld X-Patchwork-Id: 12820600 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 92570C4321E for ; Wed, 20 Apr 2022 17:15:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 061A510E23E; Wed, 20 Apr 2022 17:15:47 +0000 (UTC) Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6A17410E204; Wed, 20 Apr 2022 17:15:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650474945; x=1682010945; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=guNDvyPwv974Qjup3Gu1PjIzYBp4wwwZ0i0+sT/3RoI=; b=hw5SKZDPUlHksnYko46x8ooGoyQmeFRd9rs24JJw/C1IXjBC1G5/qHry FjSpYB4QFF7SmaPWDW8vxYtkzDCT7vrnmR7uf2Rlfuk+fFMSSy549Fbq9 tS1pP72/MiYKa6UWapDKo668TTWatS1ZWrlBo/EsocwMPa+hLJfloOscc OW+pEFIPi7y46AIhZ/5h9J564jXXbZUYJo5nb4nYEw8yG17IP3VsMIYH6 3e6N/z4XOmnULwSVOKHDGySOn9KHAuZp4le3duurB5GOyWcSAC9V4+z5Q UWYt9CNgUlTvRxTIyP5eKjiksRSBSJKOza3ey2GgBJKA9X3GkzmuPRaeV w==; X-IronPort-AV: E=McAfee;i="6400,9594,10323"; a="324537943" X-IronPort-AV: E=Sophos;i="5.90,276,1643702400"; d="scan'208";a="324537943" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Apr 2022 10:13:52 -0700 X-IronPort-AV: E=Sophos;i="5.90,276,1643702400"; d="scan'208";a="576697188" Received: from briansim-mobl.ger.corp.intel.com (HELO mwauld-desk1.intel.com) ([10.252.3.144]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Apr 2022 10:13:49 -0700 From: Matthew Auld To: intel-gfx@lists.freedesktop.org Subject: [PATCH v2] drm/doc: add rfc section for small BAR uapi Date: Wed, 20 Apr 2022 18:13:28 +0100 Message-Id: <20220420171328.57253-1-matthew.auld@intel.com> X-Mailer: git-send-email 2.34.1 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 , Lionel Landwerlin , Kenneth Graunke , Jon Bloomfield , dri-devel@lists.freedesktop.org, Daniel Vetter , mesa-dev@lists.freedesktop.org, Akeem G Abodunrin Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Add an entry for the new uapi needed for small BAR on DG2+. v2: - Some spelling fixes and other small tweaks. (Akeem & Thomas) - Rework error capture interactions, including no longer needing NEEDS_CPU_ACCESS for objects marked for capture. (Thomas) - Add probed_cpu_visible_size. (Lionel) Signed-off-by: Matthew Auld Cc: Thomas Hellström Cc: Lionel Landwerlin Cc: Jon Bloomfield Cc: Daniel Vetter Cc: Jordan Justen Cc: Kenneth Graunke Cc: Akeem G Abodunrin Cc: mesa-dev@lists.freedesktop.org --- Documentation/gpu/rfc/i915_small_bar.h | 190 +++++++++++++++++++++++ Documentation/gpu/rfc/i915_small_bar.rst | 58 +++++++ Documentation/gpu/rfc/index.rst | 4 + 3 files changed, 252 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..7bfd0cf44d35 --- /dev/null +++ b/Documentation/gpu/rfc/i915_small_bar.h @@ -0,0 +1,190 @@ +/** + * struct __drm_i915_memory_region_info - Describes one region as known to the + * driver. + * + * Note this is using both struct drm_i915_query_item and struct drm_i915_query. + * For this new query we are adding the new query id DRM_I915_QUERY_MEMORY_REGIONS + * at &drm_i915_query_item.query_id. + */ +struct __drm_i915_memory_region_info { + /** @region: The class:instance pair encoding */ + struct drm_i915_gem_memory_class_instance region; + + /** @rsvd0: MBZ */ + __u32 rsvd0; + + /** @probed_size: Memory probed by the driver (-1 = unknown) */ + __u64 probed_size; + + /** @unallocated_size: Estimate of memory remaining (-1 = unknown) */ + __u64 unallocated_size; + + union { + /** @rsvd1: MBZ */ + __u64 rsvd1[8]; + struct { + /** + * @probed_cpu_visible_size: Memory probed by the driver + * that is CPU accessible. (-1 = unknown). + * + * This will be always be <= @probed_size, and the + * remainder(if there is any) will not be CPU + * accessible. + */ + __u64 probed_cpu_visible_size; + }; + }; +}; + +/** + * struct __drm_i915_gem_create_ext - Existing gem_create behaviour, with added + * extension support using struct i915_user_extension. + * + * Note that new buffer flags should be added 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 since the kernel only supports flat-CCS on objects that can + * *only* be placed in I915_MEMORY_CLASS_DEVICE, we therefore don't + * support I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS together with + * flat-CCS. + * + * 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..be3d9bcdd86d --- /dev/null +++ b/Documentation/gpu/rfc/i915_small_bar.rst @@ -0,0 +1,58 @@ +========================== +I915 Small BAR RFC Section +========================== +Starting from DG2 we will have resizable BAR support for device local-memory(i.e +I915_MEMORY_CLASS_DEVICE), but in some cases the final BAR size might still be +smaller than the total probed_size. In such cases, only some subset of +I915_MEMORY_CLASS_DEVICE will be CPU accessible(for example the first 256M), +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. +This becomes important when placing an object in I915_MEMORY_CLASS_DEVICE, where +underneath the device has a small BAR, meaning only some portion 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 +I915_MEMORY_CLASS_DEVICE. + +.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h + :functions: __drm_i915_gem_create_ext + +probed_cpu_visible_size attribute +--------------------------------- +New struct__drm_i915_memory_region attribute which returns the total size of the +CPU accessible portion, for the particular region. This should only be +applicable for I915_MEMORY_CLASS_DEVICE. + +Vulkan will need this as part of creating a separate VkMemoryHeap with the +VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT set, to represent the CPU visible portion, +where the total size of the heap needs to be known. + +.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h + :functions: __drm_i915_memory_region_info + +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 attributes. 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 probed_cpu_visible_size of I915_MEMORY_CLASS_DEVICE +matches the probed_size. If this is not set then CPU faulting the object will +likely first require migrating the pages. + +.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h + :functions: __drm_i915_query_vma_info + +Error Capture restrictions +-------------------------- +With error capture we have two new restrictions: + + 1) Error capture is best effort on small BAR systems; if the pages are not + CPU accessible, at the time of capture, then the kernel is free to skip + trying to capture them. + + 2) On discrete we now reject error capture on recoverable contexts. In the + future the kernel may want to blit during error capture, when for example + something is not currently CPU accessible. diff --git a/Documentation/gpu/rfc/index.rst b/Documentation/gpu/rfc/index.rst index 91e93a705230..5a3bd3924ba6 100644 --- a/Documentation/gpu/rfc/index.rst +++ b/Documentation/gpu/rfc/index.rst @@ -23,3 +23,7 @@ host such documentation: .. toctree:: i915_scheduler.rst + +.. toctree:: + + i915_small_bar.rst