From patchwork Mon Oct 17 09:37:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Liu X-Patchwork-Id: 13008430 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 EE5EBC433FE for ; Mon, 17 Oct 2022 09:33:52 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id DC5BD10E3CB; Mon, 17 Oct 2022 09:33:47 +0000 (UTC) Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by gabe.freedesktop.org (Postfix) with ESMTPS id BCF3610ED0E; Mon, 17 Oct 2022 09:32:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665999151; x=1697535151; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=L0klkS76Kt8Hk/6E4tsClEGhD8s9Fs2w8vteQwCBE8U=; b=F3/6TfLJzL35a+a164pxBFAFgFAIRQKvmyBY5u6X8V5b2WfUFO+IqwNd t6nUkcRPMPdqLmUWJcKz3/MGF0yug1+MCybH0YMKFUkDh/riaa6/DY7sd FMhf5dj9cYbFIAXe3Ov7aDrlxxcI69egrFhP9Xz2KinFzujraqsf2WyEg 2NrnWjnIv3UTIAkc4dyLsGKNGEFTkwWt/DCjgfRVYlibKxH1obKRHBKHz YK7B42adFL7E8sP673f3qV4aVqkrO8o4wdu/cCc3CvgMqNjbu1YujM1iP WNcNn4Lvbpty/VS2HDOLQi18lxKkZJHXGpdQmjH5uQonTAIHxFDtur3lY w==; X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="286142604" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="286142604" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2022 02:32:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="717431229" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="717431229" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.132]) by FMSMGA003.fm.intel.com with ESMTP; 17 Oct 2022 02:32:27 -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: Mon, 17 Oct 2022 17:37:18 +0800 Message-Id: <20221017093726.2070674-3-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 Subject: [Intel-gfx] [PATCH 2/9] drm/i915: Use kmap_local_page() in gem/i915_gem_pyhs.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]. The main difference between atomic and local mappings is that local mappings doesn't disable page faults or preemption. In drm/i915/gem/i915_gem_phys.c, the functions i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() don't need to disable pagefaults and preemption for mapping because of these 2 reasons: 1. The flush operation is safe for CPU hotplug when preemption is not disabled. In drm/i915/gem/i915_gem_object.c, the functions i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() 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, i915_gem_object_get_pages_phys() and i915_gem_object_put_pages_phys() are two 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. --- drivers/gpu/drm/i915/gem/i915_gem_phys.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_phys.c b/drivers/gpu/drm/i915/gem/i915_gem_phys.c index 0d0e46dae559..d602ba19ecb2 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_phys.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_phys.c @@ -66,10 +66,10 @@ static int i915_gem_object_get_pages_phys(struct drm_i915_gem_object *obj) if (IS_ERR(page)) goto err_st; - src = kmap_atomic(page); + src = kmap_local_page(page); memcpy(dst, src, PAGE_SIZE); drm_clflush_virt_range(dst, PAGE_SIZE); - kunmap_atomic(src); + kunmap_local(src); put_page(page); dst += PAGE_SIZE; @@ -114,10 +114,10 @@ i915_gem_object_put_pages_phys(struct drm_i915_gem_object *obj, if (IS_ERR(page)) continue; - dst = kmap_atomic(page); + dst = kmap_local_page(page); drm_clflush_virt_range(src, PAGE_SIZE); memcpy(dst, src, PAGE_SIZE); - kunmap_atomic(dst); + kunmap_local(dst); set_page_dirty(page); if (obj->mm.madv == I915_MADV_WILLNEED)