From nobody Tue Apr 7 14:19:47 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 EDD74C4332F for ; Mon, 17 Oct 2022 09:33:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231373AbiJQJdZ (ORCPT ); Mon, 17 Oct 2022 05:33:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231354AbiJQJdR (ORCPT ); Mon, 17 Oct 2022 05:33:17 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 86D905A808 for ; Mon, 17 Oct 2022 02:32:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665999176; x=1697535176; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=0Ch/gzI1CiEltsWtZiZ1vnI7GDsumr0SEFm747ErScU=; b=jgCItgeC1R/Zp94KyKUhQnOWheZ9NvWIOckwNkWRHkjNznPwLqAZsUb6 MEZtEmJhJNDS2ooI4yuMy3552pwR2w0zCOKFAGQF3Tgba+HmIP943UcIp pRsLLJsbPNNuwFAlO4blrePUBbUS4WaVAG4gCs2BiIL3Ks44SMPMXVxoO An5oaMC49vxjX+zh3Kk1BQPdJn+WJvOeoxG/y5elWau+SnSCGBJTy/6vn Dv3jZTT3ENkzf62GaMbrZAC9qbQkD1fla//f6X7HfJ9CRNtilZw/dduyz gAyQSxCLx7Fkf9IxoW7wi2hpRBK8KgYDXKpNdNBQsi/2hjEnQWwpXRS6r w==; X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="305741641" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="305741641" 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 02:32:56 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="717431333" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="717431333" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.132]) by FMSMGA003.fm.intel.com with ESMTP; 17 Oct 2022 02:32:52 -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 8/9] drm/i915: Use kmap_local_page() in i915_cmd_parser.c Date: Mon, 17 Oct 2022 17:37:24 +0800 Message-Id: <20221017093726.2070674-9-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. There're 2 reasons why function copy_batch() doesn't need to disable pagefaults and preemption for mapping: 1. The flush operation is safe for CPU hotplug when preemption is not disabled. In i915_cmd_parser.c, the function copy_batch() 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, copy_batch() 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/i915_cmd_parser.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/= i915_cmd_parser.c index f93e6122f247..1a56000d7476 100644 --- a/drivers/gpu/drm/i915/i915_cmd_parser.c +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c @@ -1211,11 +1211,11 @@ static u32 *copy_batch(struct drm_i915_gem_object *= dst_obj, for (n =3D offset >> PAGE_SHIFT; remain; n++) { int len =3D min(remain, PAGE_SIZE - x); =20 - src =3D kmap_atomic(i915_gem_object_get_page(src_obj, n)); + src =3D kmap_local_page(i915_gem_object_get_page(src_obj, n)); if (src_needs_clflush) drm_clflush_virt_range(src + x, len); memcpy(ptr, src + x, len); - kunmap_atomic(src); + kunmap_local(src); =20 ptr +=3D len; remain -=3D len; --=20 2.34.1