From patchwork Sun Dec 3 13:29:43 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Liu X-Patchwork-Id: 13477326 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 7616FC46CA7 for ; Sun, 3 Dec 2023 13:18:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AB7DB10E2B1; Sun, 3 Dec 2023 13:18:26 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) by gabe.freedesktop.org (Postfix) with ESMTPS id 08FC710E2AC; Sun, 3 Dec 2023 13:18:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1701609485; x=1733145485; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=09wp7qEie3hPA9tmFNTCYBM6WHJ7/7jxnVGZAD5l5W4=; b=lrm/hR5hpRqpudchOcSjnmPOSqPJ9eDK84FNkZwpWkb9TiIL1Yxvlgys J5q6HcYOovnWgAD90CGrS2Ihi9VGVTaAqFpv+KCpeYKh2v7xPRDbg5lbR MNulsPjgTgxwA0U7PpL3OgCXIiuChfcdxvgu0lyRk0m0LpdN8P8oZtHXq 98Igxy1jvu+n8CXWhRZSzHbufpqZjKOxalKxyn1+NeER/Tob8sKhFdS4J sDABQMSBjOVhH7pZyrIoQ5ixuRFSvWsSFX042+p/dCGiltcgRoBYvFff1 uHockDwE27s0g1+J6swPCgvhYPDaeVnc4uLAoHtqHI7XUiqkiCX4kWBbE A==; X-IronPort-AV: E=McAfee;i="6600,9927,10912"; a="498239" X-IronPort-AV: E=Sophos;i="6.04,247,1695711600"; d="scan'208";a="498239" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Dec 2023 05:18:04 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10912"; a="770262426" X-IronPort-AV: E=Sophos;i="6.04,247,1695711600"; d="scan'208";a="770262426" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.36]) by orsmga002.jf.intel.com with ESMTP; 03 Dec 2023 05:18:00 -0800 From: Zhao Liu To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Ira Weiny , "Fabio M . De Francesco" , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Sun, 3 Dec 2023 21:29:43 +0800 Message-Id: <20231203132947.2328805-6-zhao1.liu@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231203132947.2328805-1-zhao1.liu@linux.intel.com> References: <20231203132947.2328805-1-zhao1.liu@linux.intel.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH v3 5/9] drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_coherency.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: Dave Hansen , Zhao Liu , Zhenyu Wang 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 (the preemption is disabled for !PREEMPT_RT case, otherwise it only disables migration).. 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_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. 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. 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_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 Reviewed-by: Ira Weiny Reviewed-by: Fabio M. De Francesco --- 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. --- .../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/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c index 3bef1beec7cb..beeb3e12eccc 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 offset, u32 v) { unsigned int needs_clflush; struct page *page; - void *map; u32 *cpu; int err; @@ -34,8 +33,7 @@ static int cpu_set(struct context *ctx, unsigned long offset, u32 v) goto out; page = i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT); - map = kmap_atomic(page); - cpu = map + offset_in_page(offset); + cpu = kmap_local_page(page) + offset_in_page(offset); 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 offset, u32 v) if (needs_clflush & CLFLUSH_AFTER) drm_clflush_virt_range(cpu, sizeof(*cpu)); - kunmap_atomic(map); + kunmap_local(cpu); i915_gem_object_finish_access(ctx->obj); out: @@ -57,7 +55,6 @@ static int cpu_get(struct context *ctx, unsigned long offset, u32 *v) { unsigned int needs_clflush; struct page *page; - void *map; u32 *cpu; int err; @@ -67,15 +64,14 @@ static int cpu_get(struct context *ctx, unsigned long offset, u32 *v) goto out; page = i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT); - map = kmap_atomic(page); - cpu = map + offset_in_page(offset); + cpu = kmap_local_page(page) + offset_in_page(offset); if (needs_clflush & CLFLUSH_BEFORE) drm_clflush_virt_range(cpu, sizeof(*cpu)); *v = *cpu; - kunmap_atomic(map); + kunmap_local(cpu); i915_gem_object_finish_access(ctx->obj); out: