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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73787C6787E for ; Mon, 8 Oct 2018 02:25:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30497206B2 for ; Mon, 8 Oct 2018 02:25:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JHFeVw81" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30497206B2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726295AbeJHJez (ORCPT ); Mon, 8 Oct 2018 05:34:55 -0400 Received: from mail-ed1-f66.google.com ([209.85.208.66]:40519 "EHLO mail-ed1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725760AbeJHJez (ORCPT ); Mon, 8 Oct 2018 05:34:55 -0400 Received: by mail-ed1-f66.google.com with SMTP id r1-v6so1714908edd.7; Sun, 07 Oct 2018 19:25:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-disposition:in-reply-to:user-agent; bh=dUKWP42tSEj4nZi5aNXIZNIm0AG5L6jzWxC0b78pWGc=; b=JHFeVw81IYVtzBGehC7cBAwhXeONXqQqLwDQf6SF6x8RX+e1eZhA90c12UQYYL0ShZ nylg6ESV16ARkcMJTry6HMR96SpiPfcJLD+cdJVvHIDjXpyyF6OUITUPg1NDUqLivrOn Oj7IcB5anPx983K7xbUIohNFaGcSV8LOI9sLnq4dxQaBvkoISb6SdwgN60j8KuLFl6MO ghKIMOZ2wwTur8EWtus7Nuf6nUD6MGGQRJQyeEddRrxZRK9d4YxZptcTLYq7DP/MO2Ew fQV5/PsPJnLyolNEl3z4GFYSelhaFofJSV5+MXaRPb5a21WCW5uhlZ63GPhUmnl/CFHZ D3Mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:reply-to :references:mime-version:content-disposition:in-reply-to:user-agent; bh=dUKWP42tSEj4nZi5aNXIZNIm0AG5L6jzWxC0b78pWGc=; b=VJMt8J5bGbRB+gk61H0Jm1ZmiwD2ciK7bCZ+2b8mpVENBdvuyuIp2dgVJTzCki5DxX vWPzYGuaQmLqnZvhTtSU886a+vGbxNBKJ5GXFY5O8teLkI7359G9tJISDkUWUs/xHDjo I6oZJWpDHkwng/ZvMq5/F4ryWr+R7VilZFf1HZeu75DnFNueddN+vkayds4zImJNSr4R 8uOqwaiGxD5K1rX9lEeENBbSxBpDr8CjVkOzwUH3klphciUYQa/eFqaM/SkrKaUJOKV5 FZIACwGULW9dAyaAC49/EOTMTZQ7a3+9v5DupzvfmGWAeBi25DoFmr/H7PUJVoe5IyvY lp8Q== X-Gm-Message-State: ABuFfoiy5C6qHerh+6+SFwS3Z1kDG7G3twDkhvuYFkeXLVHyqW5MtJOb F5zk4ZMcBOgCFDeNt0q7U1Q= X-Google-Smtp-Source: ACcGV63tP4FNDWbQf5BcKk1+FBvdPV24G25AFWR1bib5s7n8xNpJZ6J4w6Q1oGXzkw2eMCzzaAwN6g== X-Received: by 2002:a17:906:e1ce:: with SMTP id gp14-v6mr14776661ejb.221.1538965533714; Sun, 07 Oct 2018 19:25:33 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id g48-v6sm5184406edc.93.2018.10.07.19.25.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 07 Oct 2018 19:25:32 -0700 (PDT) Date: Mon, 8 Oct 2018 02:25:32 +0000 From: Wei Yang To: peng.hao2@zte.com.cn Cc: richard.weiyang@gmail.com, penghao122@sina.com.cn, pbonzini@redhat.com, rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, joro@8bytes.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] kvm/x86 : avoid shifting signed 32-bit value by 31 bits Message-ID: <20181008022532.4ve2xww4yphk6f5d@master> Reply-To: Wei Yang References: <20181006070849.psgrrhiysnrytbjr@master> <201810080904344038939@zte.com.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201810080904344038939@zte.com.cn> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 08, 2018 at 09:04:34AM +0800, peng.hao2@zte.com.cn wrote: >>On Sat, Oct 06, 2018 at 11:31:04AM +0800, peng.hao2@zte.com.cn wrote: >>>>On Thu, Oct 04, 2018 at 01:47:18PM -0400, Peng Hao wrote: >>>>> >>>>>From: Peng Hao >>>>> >>>>> modify AVIC_LOGICAL_ID_ENTRY_VALID_MASK to unsigned >>>>> >>>>>Signed-off-by: Peng Hao >>>>>--- >>>>> arch/x86/kvm/svm.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>>diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >>>>>index d96092b..bf1ded4 100644 >>>>>--- a/arch/x86/kvm/svm.c >>>>>+++ b/arch/x86/kvm/svm.c >>>>>@@ -262,7 +262,7 @@ struct amd_svm_iommu_ir { >>>>> }; >>>>> >>>>> #define AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK (0xFF) >>>>>-#define AVIC_LOGICAL_ID_ENTRY_VALID_MASK (1 << 31) >>>>>+#define AVIC_LOGICAL_ID_ENTRY_VALID_MASK (1UL << 31) >>> >>>>It is reasonable to change to unsigned, while not necessary to unsigned >>>>long? >>>AVIC_LOGICAL_ID_ENTRY_VALID_MASK is used in function avic_ldr_write. >>>here I think it doesn't matter if you use unsigned or unsigned long. Do you have any suggestions? > >>In current case, AVIC_LOGICAL_ID_ENTRY_VALID_MASK is used to calculate >>the value of new_entry with type of u32. So the definition here is not >>harmful. > >>Also, I did a quick grep and found similar definition (1 << 31) is popular >>in the whole kernel tree. > >>The reason to make this change is not that strong to me. Would you >>minding sharing more reason behind this change? >oh, I'm just thinking logically, not more reason. This definition may introduce problem when this value is used to calculate a 64bit data. Since current entry is 32bit, we may leave it as it is for now. -- Wei Yang Help you, Help me