From nobody Tue Apr 7 14:19:08 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 989FAC43217 for ; Mon, 17 Oct 2022 09:32:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231313AbiJQJcx (ORCPT ); Mon, 17 Oct 2022 05:32:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231317AbiJQJcn (ORCPT ); Mon, 17 Oct 2022 05:32:43 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C95B58DD6 for ; Mon, 17 Oct 2022 02:32:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665999160; x=1697535160; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ZXOTrqnB1S2hiIrW6AdSeUKTfgzUpr1fFCYC+QaCffw=; b=ZBVwtOMGjrVr/Cz2gSBb3HB2GjVyFD7+JWmQLxCVebjsKl9DAgl7YpPt 3aMUVr4eAKuZFIVzGNxsy0Gv2mOr3nF+hcrazTVmdiQkVmHlyFCyeZet+ go+nOOlgUjQeGjbp5ioISj6r1FrAgAlN+HEGEeun8O+AiAQXNkLA99cv4 VpzaMc6Nzwe/WCTlyS3XBXIG0yKjaNK6oIcbPoFmckcs/K/5vZOC0PS8U BRHsMo5Ze2MQdZMksRnSJ6eIn9f5whqe1nWMeujyJiwxCiA+6o+FiKhsF QHXSG6ED1SuY2J62KZg3FwJc4Murj2fNefBEsek8n94BYaYkigU3EXRnB Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="305741593" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="305741593" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2022 02:32:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="717431262" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="717431262" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.132]) by FMSMGA003.fm.intel.com with ESMTP; 17 Oct 2022 02:32:35 -0700 From: Zhao Liu To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matthew Auld , =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Nirmoy Das , Maarten Lankhorst , Chris Wilson , =?UTF-8?q?Christian=20K=C3=B6nig?= , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: Ira Weiny , "Fabio M . De Francesco" , Zhenyu Wang , Zhao Liu , Dave Hansen Subject: [PATCH 4/9] drm/i915: Use kmap_local_page() in gem/selftests/huge_pages.c Date: Mon, 17 Oct 2022 17:37:20 +0800 Message-Id: <20221017093726.2070674-5-zhao1.liu@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221017093726.2070674-1-zhao1.liu@linux.intel.com> References: <20221017093726.2070674-1-zhao1.liu@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Zhao Liu The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1]. The main difference between atomic and local mappings is that local mappings doesn't disable page faults or preemption. In drm/i915/gem/selftests/huge_pages.c, function __cpu_check_shmem() mainly uses mapping to flush cache and check the value. There're 2 reasons why __cpu_check_shmem() doesn't need to disable pagefaults and preemption for mapping: 1. The flush operation is safe for CPU hotplug when preemption is not disabled. Function __cpu_check_shmem() calls drm_clflush_virt_range() to use CLFLUSHOPT or WBINVD to flush. Since CLFLUSHOPT is global on x86 and WBINVD is called on each cpu in drm_clflush_virt_range(), the flush operation is global and any issue with cpu's being added or removed can be handled safely. 2. Any context switch caused by preemption or sleep (pagefault may cause sleep) doesn't affect the validity of local mapping. Therefore, __cpu_check_shmem() is a function where the use of kmap_local_page() in place of kmap_atomic() is correctly suited. Convert the calls of kmap_atomic() / kunmap_atomic() to kmap_local_page() / kunmap_local(). [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com Suggested-by: Dave Hansen Suggested-by: Ira Weiny Suggested-by: Fabio M. De Francesco Signed-off-by: Zhao Liu --- Suggested by credits: Dave: Referred to his explanation about cache flush. Ira: Referred to his task document, review comments and explanation about cache flush. Fabio: Referred to his boiler plate commit message. --- drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/= drm/i915/gem/selftests/huge_pages.c index c570cf780079..6f4efe905105 100644 --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c @@ -1022,7 +1022,7 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, u3= 2 dword, u32 val) goto err_unlock; =20 for (n =3D 0; n < obj->base.size >> PAGE_SHIFT; ++n) { - u32 *ptr =3D kmap_atomic(i915_gem_object_get_page(obj, n)); + u32 *ptr =3D kmap_local_page(i915_gem_object_get_page(obj, n)); =20 if (needs_flush & CLFLUSH_BEFORE) drm_clflush_virt_range(ptr, PAGE_SIZE); @@ -1030,12 +1030,12 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, = u32 dword, u32 val) if (ptr[dword] !=3D val) { pr_err("n=3D%lu ptr[%u]=3D%u, val=3D%u\n", n, dword, ptr[dword], val); - kunmap_atomic(ptr); + kunmap_local(ptr); err =3D -EINVAL; break; } =20 - kunmap_atomic(ptr); + kunmap_local(ptr); } =20 i915_gem_object_finish_access(obj); --=20 2.34.1