From patchwork Wed Mar 29 07:32:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Liu X-Patchwork-Id: 13192035 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 0C9E4C761AF for ; Wed, 29 Mar 2023 07:25:05 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 544BC10E4D5; Wed, 29 Mar 2023 07:25:04 +0000 (UTC) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id BCB5410E4FE; Wed, 29 Mar 2023 07:25:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680074700; x=1711610700; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=GMpKo8ThZ2YBrIiNDv5DIUoRW6Piin/4x6sH+rZpkMU=; b=N8SOof7zkbbECzwuzNHEYGNELDAnjm5FRzrTaUH5Vn4ILm5YOuPPd4u3 ttZa/H3J04Wf/rFzSypUwdJtxSnserWGnIkCLKbSMOFzim5LHBp2XhwU7 BMbPG2mwwaL7IUpgwgzBg+RIyzAoeNt2dgaZb/XOFxZ6yuJINj7qthM6R xtjdnZc2il0tckucZ90KWT4MNkGPZCOmJgC5nadikl1nBUFKJ3EmxsGJz DcPotdxbUzHDveF8w9QroLy4Eltnr4zqUnvqIqFu8OQEHyr7u+J83g2w8 CNF1uylvzPYib24AMAFbHJlMCFanf2DJ0IJnTUIuTbwr48oKovs3hfHkQ A==; X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="405746130" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="405746130" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2023 00:24:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="684160621" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="684160621" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.112]) by orsmga002.jf.intel.com with ESMTP; 29 Mar 2023 00:24:40 -0700 From: Zhao Liu To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matthew Auld , =?utf-8?q?Thomas_Hellstr=C3=B6m?= , Nirmoy Das , Maarten Lankhorst , Chris Wilson , =?utf-8?q?Christian_K=C3=B6nig?= , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Wed, 29 Mar 2023 15:32:17 +0800 Message-Id: <20230329073220.3982460-7-zhao1.liu@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230329073220.3982460-1-zhao1.liu@linux.intel.com> References: <20230329073220.3982460-1-zhao1.liu@linux.intel.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH v2 6/9] drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_context.c X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Fabio M . De Francesco" , Ira Weiny , Zhao Liu , Zhenyu Wang , Dave Hansen Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" From: Zhao Liu The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1], and this patch converts the call from kmap_atomic() to kmap_local_page(). The main difference between atomic and local mappings is that local mappings doesn't disable page faults or preemption. With kmap_local_page(), we can avoid the often unwanted side effect of unnecessary page faults or preemption disables. In drm/i915/gem/selftests/i915_gem_context.c, functions cpu_fill() and cpu_check() mainly uses mapping to flush cache and check/assign the value. There're 2 reasons why cpu_fill() and cpu_check() don't need to disable pagefaults and preemption for mapping: 1. The flush operation is safe. cpu_fill() and cpu_check() 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. 2. Any context switch caused by preemption or page faults (page fault may cause sleep) doesn't affect the validity of local mapping. Therefore, cpu_fill() and cpu_check() 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 v2: * Dropped hot plug related description since it has nothing to do with kmap_local_page(). * No code change since v1, and added description of the motivation of using kmap_local_page(). Suggested-by: Dave Hansen Suggested-by: Ira Weiny Suggested-by: Fabio M. De Francesco Signed-off-by: Zhao Liu Reviewed-by: Ira Weiny --- 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 and his description about why kmap_local_page() should be preferred. --- drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c index a81fa6a20f5a..dcbc0b8e3323 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c @@ -481,12 +481,12 @@ static int cpu_fill(struct drm_i915_gem_object *obj, u32 value) for (n = 0; n < real_page_count(obj); n++) { u32 *map; - map = kmap_atomic(i915_gem_object_get_page(obj, n)); + map = kmap_local_page(i915_gem_object_get_page(obj, n)); for (m = 0; m < DW_PER_PAGE; m++) map[m] = value; if (!has_llc) drm_clflush_virt_range(map, PAGE_SIZE); - kunmap_atomic(map); + kunmap_local(map); } i915_gem_object_finish_access(obj); @@ -512,7 +512,7 @@ static noinline int cpu_check(struct drm_i915_gem_object *obj, for (n = 0; n < real_page_count(obj); n++) { u32 *map, m; - map = kmap_atomic(i915_gem_object_get_page(obj, n)); + map = kmap_local_page(i915_gem_object_get_page(obj, n)); if (needs_flush & CLFLUSH_BEFORE) drm_clflush_virt_range(map, PAGE_SIZE); @@ -538,7 +538,7 @@ static noinline int cpu_check(struct drm_i915_gem_object *obj, } out_unmap: - kunmap_atomic(map); + kunmap_local(map); if (err) break; }