From patchwork Tue Feb 1 18:24:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Bob Beckett X-Patchwork-Id: 12732135 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 696FEC433EF for ; Tue, 1 Feb 2022 18:24:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8BC7C10E1A7; Tue, 1 Feb 2022 18:24:46 +0000 (UTC) Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3405E10E1EE; Tue, 1 Feb 2022 18:24:45 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: bbeckett) with ESMTPSA id 977C61F42EBA DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1643739884; bh=7xQvHqE5JkxFe/B6GU5XOuYuw6gmCUNHi1lLN9/W+eo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cWLBVvLvz7F3DTluAwHv2J0e088LXGdJyggbPFHZlSLY3r0ML4Y457PgbRc72jBCO 1Ysge5sVWV/e7iSVD4YHXiHFiaZbVhjBhlCD9mriUk5U0787fTtzEJK0SsGrT2aTHn YieTj097gV0o7dJoDJaxR1dxO2xQz8HHWEBh5FE3/e3kRQkGBR2RKd0nhKDGMBkdst 9NBIbZNWPNQ9INCpxsv0sll/EEILjENbgJT8CZKP/AQfL7Imj4gaBrE3NwQxJylf1x zw1GdfWLV7rysQ3kxXEXR57tfg9T1WSQ5dkEJEGLGHGQgh5RjIZ2Jem5TQWKBBRD9w WBRjbmesA3y6Q== From: Robert Beckett To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter Subject: [PATCH v7 5/5] drm/i915/uapi: document behaviour for DG2 64K support Date: Tue, 1 Feb 2022 18:24:21 +0000 Message-Id: <20220201182422.1548863-6-bob.beckett@collabora.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220201182422.1548863-1-bob.beckett@collabora.com> References: <20220201182422.1548863-1-bob.beckett@collabora.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: Robert Beckett , =?utf-8?q?Thomas_Hellstr?= =?utf-8?q?=C3=B6m?= , dri-devel@lists.freedesktop.org, Jordan Justen , intel-gfx@lists.freedesktop.org, Kenneth Graunke , Tony Ye , Slawomir Milczarek , Matthew Auld , mesa-dev@lists.freedesktop.org, linux-kernel@vger.kernel.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. 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 | 44 ++++++++++++++++++++++++++++++++----- 1 file changed, 39 insertions(+), 5 deletions(-) diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h index 5e678917da70..77e5e74c32c1 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; @@ -3145,11 +3151,39 @@ 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. 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; /**