From nobody Tue Apr 7 14:19:07 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 65C8EC4332F for ; Mon, 17 Oct 2022 09:32:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230087AbiJQJc4 (ORCPT ); Mon, 17 Oct 2022 05:32:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231298AbiJQJcp (ORCPT ); Mon, 17 Oct 2022 05:32:45 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28B9446632 for ; Mon, 17 Oct 2022 02:32:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665999164; x=1697535164; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Qa17WTfuPuByL/pGxqJjZfPv2fBRDy/8RHd7BwsgD1E=; b=AoE485pcIrMn+qUcfTmyZ55ZUcGRRjDdAIMlg6nPbId6mCkR1PMayGiX yA/4Y5zJ/4Ko50nVGRf6C0M3SKP3bauloEu1bOOZGxc4JbytLDEHqPg+p gBMQOP9+3Oi8N+UHAqoF1GgZyHnpHGS0vY6ySVHZHKUr27xmHJK4cmMoP 3ByHnNk6/fCOW45oruW1uDTra2wTji9BxhkKWv57iDKYou7imQtZPBcno eIHiF2sg4otnbT8Y5UsUF1+hORorSWENHr1fzK/VvLzl3qUwRIJXvG8ys VsVwPgP21LGHWIx9a2oA3DW4gG9xJSylEUucX6MsDd2Tlb2eZJu8TiUsx Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="305741608" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="305741608" 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 02:32:43 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="717431281" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="717431281" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.132]) by FMSMGA003.fm.intel.com with ESMTP; 17 Oct 2022 02:32:39 -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 5/9] drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_coherency.c Date: Mon, 17 Oct 2022 17:37:21 +0800 Message-Id: <20221017093726.2070674-6-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/i915_gem_coherency.c, functions cpu_set() and cpu_get() mainly uses mapping to flush cache and assign the value. There're 2 reasons why cpu_set() and cpu_get() don't need to disable pagefaults and preemption for mapping: 1. The flush operation is safe for CPU hotplug when preemption is not disabled. cpu_set() and cpu_get() call 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_set() and cpu_get() are functions 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. --- .../gpu/drm/i915/gem/selftests/i915_gem_coherency.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c b/driv= ers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c index a666d7e610f5..b12402c74424 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c @@ -24,7 +24,6 @@ static int cpu_set(struct context *ctx, unsigned long off= set, u32 v) { unsigned int needs_clflush; struct page *page; - void *map; u32 *cpu; int err; =20 @@ -34,8 +33,7 @@ static int cpu_set(struct context *ctx, unsigned long off= set, u32 v) goto out; =20 page =3D i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT); - map =3D kmap_atomic(page); - cpu =3D map + offset_in_page(offset); + cpu =3D kmap_local_page(page) + offset_in_page(offset); =20 if (needs_clflush & CLFLUSH_BEFORE) drm_clflush_virt_range(cpu, sizeof(*cpu)); @@ -45,7 +43,7 @@ static int cpu_set(struct context *ctx, unsigned long off= set, u32 v) if (needs_clflush & CLFLUSH_AFTER) drm_clflush_virt_range(cpu, sizeof(*cpu)); =20 - kunmap_atomic(map); + kunmap_local(cpu); i915_gem_object_finish_access(ctx->obj); =20 out: @@ -57,7 +55,6 @@ static int cpu_get(struct context *ctx, unsigned long off= set, u32 *v) { unsigned int needs_clflush; struct page *page; - void *map; u32 *cpu; int err; =20 @@ -67,15 +64,14 @@ static int cpu_get(struct context *ctx, unsigned long o= ffset, u32 *v) goto out; =20 page =3D i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT); - map =3D kmap_atomic(page); - cpu =3D map + offset_in_page(offset); + cpu =3D kmap_local_page(page) + offset_in_page(offset); =20 if (needs_clflush & CLFLUSH_BEFORE) drm_clflush_virt_range(cpu, sizeof(*cpu)); =20 *v =3D *cpu; =20 - kunmap_atomic(map); + kunmap_local(cpu); i915_gem_object_finish_access(ctx->obj); =20 out: --=20 2.34.1