From mboxrd@z Thu Jan 1 00:00:00 1970 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 3C3A3C38145 for ; Thu, 8 Sep 2022 17:41:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232326AbiIHRlb (ORCPT ); Thu, 8 Sep 2022 13:41:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231827AbiIHRk7 (ORCPT ); Thu, 8 Sep 2022 13:40:59 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC40C2DE3 for ; Thu, 8 Sep 2022 10:39:38 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id f24so18643014plr.1 for ; Thu, 08 Sep 2022 10:39:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=Ibf2Rs7XFT5ZnX84v5i/nCzDWYA2lLRXva8K8FpnKaE=; b=Y1apfqUNpBKh81zUqjNz1zjMg6kCkBJJJN9WteQ+RsktQ/RnDF/aJpbfaW7HhGImBW I6P4aLNQbSdMkhGytc09SCNTDoZ3YoqMzr/CFGx2sfHPm69nyrOtmXodhGug7ygKWe5q iGC2Etc7Q3+g1DEFu5gFNnwLPnvsKO3TUpxyxgsWTUpTWZhWVEB8OKz4yYBb56GD21mY JIRMd1p4V2v8sYhkTCyBTM+uTv5Wpg7um3AB/xvrKBxiFWk4spYPyNhr2ZAQQY1S/D/8 KrBjQEwqY/9MjDJvgRgp5HSQ0Kn/Z9NVJ6Tx8fj4Pj9OUEQ9cM5m+6hfcDk1qsjIunoX sfMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=Ibf2Rs7XFT5ZnX84v5i/nCzDWYA2lLRXva8K8FpnKaE=; b=ymIDsTtGZ5dyoCvxO+/DNIh9RQwPz7pQwKwqrkSWiYSq+8n7rRZX7+WXDT7be9sQzE R2kfkIF6cDYShFo7rYautWiivV3VfRS3Y8zq0GdtvPpr0r5HqT+bV5hEQxLE2Rj/Iipi XFdtACHJmqBKSd21NhvcBCBc6qbE8gJhIS9yr/zDfCsHp1nlvSfcuXJhuLQyk6h2LnwY TIuigKKYb0TAw476QGtXj4sJmk+Pc2WnWXVMdVqhXt3FjqqOj7799bkUcfTdKyqJk52x nOAxKEtXhUlrHKvqz4IMn3/QBjczTP4VI5KPtBWeKQar7AjUixj3WITDoUtLJv/s7GmT pJQw== X-Gm-Message-State: ACgBeo3dF0J4NtSMUXK/vEJz2bUA7Na0WaI+RswxetJlDvUHgacUdK2I aHMzvRQ1med8ROMKQKpEpY7+9w== X-Google-Smtp-Source: AA6agR42smilAfgdcEGqi/GQJRCr5wSe+lozghtjTz9mRCUatdQBZeBUjvQ2+qaawU0RYByIr+/NIw== X-Received: by 2002:a17:90b:1c8f:b0:1fb:9d43:8ecf with SMTP id oo15-20020a17090b1c8f00b001fb9d438ecfmr5439682pjb.160.1662658776881; Thu, 08 Sep 2022 10:39:36 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id o15-20020a170902d4cf00b00173411a4385sm4599069plg.43.2022.09.08.10.39.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Sep 2022 10:39:36 -0700 (PDT) Date: Thu, 8 Sep 2022 17:39:32 +0000 From: Sean Christopherson To: cgel.zte@gmail.com Cc: pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, ye xingchen , Zeal Robot Subject: Re: [PATCH linux-next] KVM:define vcpu_get_pid_fops with DEFINE_DEBUGFS_ATTRIBUTE Message-ID: References: <20220815031228.64126-1-ye.xingchen@zte.com.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220815031228.64126-1-ye.xingchen@zte.com.cn> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 15, 2022, cgel.zte@gmail.com wrote: > From: ye xingchen > > From the coccinelle check: > ./virt/kvm/kvm_main.c line 3847 > WARNING vcpu_get_pid_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > Reported-by: Zeal Robot > Signed-off-by: ye xingchen > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 515dfe9d3bcf..a0817179f8e4 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3844,7 +3844,7 @@ static int vcpu_get_pid(void *data, u64 *val) > return 0; > } > > -DEFINE_SIMPLE_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); > +DEFINE_DEBUGFS_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); Based on the comments in scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci, it seems that using DEFINE_DEBUGFS_ATTRIBUTE is only beneficial if the file is created with debugfs_create_file_unsafe(). IIUC, using DEFINE_DEBUGFS_ATTRIBUTE without switching to debugfs_create_file_unsafe() will actually _add_ overhead. //# Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file() //# imposes some significant overhead as compared to //# DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe(). Using DEFINE_DEBUGFS_ATTRIBUTE also effectively drops ->llseek() support. I assume that's not a problem? But someone that knows how this is actually used should chime in.