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[23.128.96.18]) by mx.google.com with ESMTP id f13si4513653pgv.730.2022.01.20.13.24.19; Thu, 20 Jan 2022 13:24:32 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@collabora.com header.s=mail header.b=DyPU9PXk; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=collabora.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347730AbiARRxs (ORCPT + 99 others); Tue, 18 Jan 2022 12:53:48 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:39860 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347631AbiARRxk (ORCPT ); Tue, 18 Jan 2022 12:53:40 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: bbeckett) with ESMTPSA id E3C891F43F91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1642528419; bh=ZPlwOY+VgFIW9bHeyG/JUeeqGePchWBvBOtEUiWKy3I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DyPU9PXksdffKxY7Ta1zW9QlKCUVAuJ4P+lcAriv5Hy0Udy9vRrEsQAjWaGAoWlPO NbaBGQ3pLb/MDcBqEQUtkfhnzQnZ3NinU0Je2UG+uUGcTyiWRP0rRCSfmbeBeFVkUO Jm2/J3xzCIJuKvI4Ot3+GDKD86+3OCBJ4zPXyuAZ+gBn1jaU7HpnlkICEObwclIGQp rRK1J526JtjSdELf2QqOdTyAFWxSZTGg5UlNXfX63xMyxkh0m0OG9ryWlN4hpx62AW 8T+cHr8WKoB3nJd466j7xUTRbClW5cYXQZT+eVEBQGmwna17Adp/rwRjh8KtDn2mF8 bmWcUp5MkRgVg== From: Robert Beckett To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter Cc: Matthew Auld , Ramalingam C , Robert Beckett , Simon Ser , Pekka Paalanen , Jordan Justen , Kenneth Graunke , mesa-dev@lists.freedesktop.org, Tony Ye , Slawomir Milczarek , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] drm/i915/uapi: document behaviour for DG2 64K support Date: Tue, 18 Jan 2022 17:50:37 +0000 Message-Id: <20220118175036.3840934-5-bob.beckett@collabora.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220118175036.3840934-1-bob.beckett@collabora.com> References: <20220118175036.3840934-1-bob.beckett@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. v2: Fixed suggestions on formatting [Daniel] Signed-off-by: Matthew Auld Signed-off-by: Ramalingam C Signed-off-by: Robert Beckett 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..486b7b96291e 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 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 GD2, this + * id deemed to be a good compromise. */ __u64 size; /** -- 2.25.1