From patchwork Fri Feb 18 18:47:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Ramalingam C X-Patchwork-Id: 12751800 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 AB7FAC433EF for ; Fri, 18 Feb 2022 18:48:32 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2E0B210E911; Fri, 18 Feb 2022 18:48:23 +0000 (UTC) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by gabe.freedesktop.org (Postfix) with ESMTPS id C590910E8EE; Fri, 18 Feb 2022 18:48:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1645210096; x=1676746096; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=A1Py057cgx8vK/xPqhYzp1XVx50RaQUDPsgswyL714g=; b=FgKPE69D9ZVjPm6jQbMewGFgfWyqpk2VFaNWhBLxftgDeSA3ayGAXBkb eL/3Rjk+iJPgjw+d4enf3d6LzjAMP+6RtkD+qD3p9YMqTIiZ57mRoZWFK 4sdWWfeNwmlls8AM1ak8Ex3ZcZXole0/4Q/NkJYh/DxOpYI3jdclZ9NAZ v5OfqmAKhuyAyzoZFVNeRPzI+oocAXK7cwNq5mBIAdoKhSkT3cdhsqaoL 7jgjVsGKG5LqZxSMidvlYrhwxn5FdqARWjxO+yJfCGBX845WWKXQFISNB UVnQVhI8zEt1rXWZYwY7jeJm81hHDr/xE5Zy6iJbGQFmWG9e983EYh6rx g==; X-IronPort-AV: E=McAfee;i="6200,9189,10262"; a="251388808" X-IronPort-AV: E=Sophos;i="5.88,379,1635231600"; d="scan'208";a="251388808" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2022 10:48:16 -0800 X-IronPort-AV: E=Sophos;i="5.88,379,1635231600"; d="scan'208";a="489642384" Received: from ramaling-i9x.iind.intel.com ([10.203.144.108]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2022 10:48:10 -0800 From: Ramalingam C To: intel-gfx , dri-devel Subject: [PATCH 12/15] drm/i915/uapi: document behaviour for DG2 64K support Date: Sat, 19 Feb 2022 00:17:49 +0530 Message-Id: <20220218184752.7524-13-ramalingam.c@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20220218184752.7524-1-ramalingam.c@intel.com> References: <20220218184752.7524-1-ramalingam.c@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: Tony Ye , =?utf-8?q?Thomas_Hellstr=C3=B6m?= , lucas.demarchi@intel.com, Kenneth Graunke , Slawomir Milczarek , Matthew Auld , Jordan Justen , mesa-dev@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Matthew Auld On discrete platforms like DG2, we need to support a minimum page size of 64K when dealing with device local-memory. This is quite tricky for various reasons, so try to document the new implicit uapi for this. v4: Kdoc modification. v3: fix typos and less emphasis v2: Fixed suggestions on formatting [Daniel] Signed-off-by: Matthew Auld Signed-off-by: Ramalingam C Signed-off-by: Robert Beckett Acked-by: Jordan Justen Reviewed-by: Ramalingam C Reviewed-by: Thomas Hellström cc: Simon Ser cc: Pekka Paalanen Cc: Jordan Justen Cc: Kenneth Graunke Cc: mesa-dev@lists.freedesktop.org Cc: Tony Ye Cc: Slawomir Milczarek --- include/uapi/drm/i915_drm.h | 45 ++++++++++++++++++++++++++++++++----- 1 file changed, 40 insertions(+), 5 deletions(-) diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h index 914ebd9290e5..05c3642aaece 100644 --- a/include/uapi/drm/i915_drm.h +++ b/include/uapi/drm/i915_drm.h @@ -1118,10 +1118,16 @@ struct drm_i915_gem_exec_object2 { /** * When the EXEC_OBJECT_PINNED flag is specified this is populated by * the user with the GTT offset at which this object will be pinned. + * * When the I915_EXEC_NO_RELOC flag is specified this must contain the * presumed_offset of the object. + * * During execbuffer2 the kernel populates it with the value of the * current GTT offset of the object, for future presumed_offset writes. + * + * See struct drm_i915_gem_create_ext for the rules when dealing with + * alignment restrictions with I915_MEMORY_CLASS_DEVICE, on devices with + * minimum page sizes, like DG2. */ __u64 offset; @@ -3144,11 +3150,40 @@ struct drm_i915_gem_create_ext { * * 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. + * + * DG2 64K min page size implications: + * + * On discrete platforms, starting from DG2, we have to contend with GTT + * page size restrictions when dealing with I915_MEMORY_CLASS_DEVICE + * objects. Specifically the hardware only supports 64K or larger GTT + * page sizes for such memory. The kernel will already ensure that all + * I915_MEMORY_CLASS_DEVICE memory is allocated using 64K or larger page + * sizes underneath. + * + * Note that the returned size here will always reflect any required + * rounding up done by the kernel, i.e 4K will now become 64K on devices + * such as DG2. + * + * Special DG2 GTT address alignment requirement: + * + * The GTT alignment will also need to be at least 2M for such objects. + * + * Note that due to how the hardware implements 64K GTT page support, we + * have some further complications: + * + * 1) The entire PDE (which covers a 2MB virtual address range), must + * contain only 64K PTEs, i.e mixing 4K and 64K PTEs in the same + * PDE is forbidden by the hardware. + * + * 2) We still need to support 4K PTEs for I915_MEMORY_CLASS_SYSTEM + * objects. + * + * To keep things simple for userland, we mandate that any GTT mappings + * must be aligned to and rounded up to 2MB. The kernel will internally + * pad them out to the next 2MB boundary. As this only wastes virtual + * address space and avoids userland having to copy any needlessly + * complicated PDE sharing scheme (coloring) and only affects DG2, this + * is deemed to be a good compromise. */ __u64 size; /**