From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="N+fHmNuM" Received: from mail-pg1-x549.google.com (mail-pg1-x549.google.com [IPv6:2607:f8b0:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F18531A6 for ; Fri, 1 Dec 2023 07:56:02 -0800 (PST) Received: by mail-pg1-x549.google.com with SMTP id 41be03b00d2f7-5c1b986082dso643240a12.0 for ; Fri, 01 Dec 2023 07:56:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1701446162; x=1702050962; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=T+9aLJpGyu0Q/y7mwBTnwWcmuz7X2zXjBIdqmSWvzkk=; b=N+fHmNuMBdBuSJAJex97iOFcMfroAQEN/7g7vNKNXNAV0S6RUHvPifwMoN76hVOmJC V149BgvgugDmsGkVBQnvxBE1tSVx0MbVN925TdBNs7xG2AtbXFY0SjwVL5+cY5CExXgn l8iiBKXoU10Bc+e7wWl2ONL9liXD44bIU3rfkqhSWKpAzjo27dtjvYVELt44JD1VfkWP Q08WGTnTn8SLD62ZhO/MoBFpq/Kr3Ez/gOH0oKtimJV8J9mLTKDSmPWQJjt/EXdJnMEt 6rnxh6QEb46atpv1qmq0+cLdNwMVvVjJc6ucVIy5sDL7m1yv9Yp2ox8gqjL9wi5r4tAT 6txQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701446162; x=1702050962; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=T+9aLJpGyu0Q/y7mwBTnwWcmuz7X2zXjBIdqmSWvzkk=; b=jiPsez2MphwmQpR1eNRQwYB4rQb2QPDCwKHZS9pt5BIADtT3vxSZNLpNnNDd/2Bk7s KqCInLeWUXbX+RGJUvkp5oCvHzJZ3C+0tgElKy4SqTFhAsSnAdj2hUK2yFxg4z0EyNfg yHlvFY3EhJ64Az9omtlNJMdKSWuzDotxxuncj7uLeHOR9yxst9q6UV7Jk1Y1WKnyiVxG ekmIKR/w/+zjDJnaKdxSEclUWvIJkoDN2XVpW2PDMyRYUCn9iRB+NBpg/ZByIBhjLGm0 QxnOjfFB5M1UfFTTlCkcFG+ZJW0/DH0k7A5LpQHMDOxWasFbcOje+HBq7FEtiws9wLaK Ig8Q== X-Gm-Message-State: AOJu0YzSBBBvSZoItmvwgIzMWL0SAxczmeuQJ5iQmYJc8k4WVTAtO6xQ 2ngmmP+MEFh4qTVquzSydqlTZEBPzkg= X-Google-Smtp-Source: AGHT+IEIZp/UjGQmIqcjxLcrjtAVgVHJtCowAaXJ8Z6oo7dg35tnLSRyZWGu2wbxgV7cxavSU+m4ulAH0aE= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a63:5c0f:0:b0:5c6:504:7e22 with SMTP id q15-20020a635c0f000000b005c605047e22mr1192330pgb.5.1701446162412; Fri, 01 Dec 2023 07:56:02 -0800 (PST) Date: Fri, 1 Dec 2023 07:56:01 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <202311302231.sinLrAig-lkp@intel.com> <87v89jmc3q.fsf@redhat.com> Message-ID: Subject: Re: arch/x86/kvm/vmx/hyperv.h:79:30: sparse: sparse: cast truncates bits from constant value (1b009b becomes 9b) From: Sean Christopherson To: Yujie Liu Cc: Vitaly Kuznetsov , kernel test robot , oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, Paolo Bonzini , kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, Dec 01, 2023, Yujie Liu wrote: > On Thu, Nov 30, 2023 at 09:49:43AM -0800, Sean Christopherson wrote: > > On Thu, Nov 30, 2023, Vitaly Kuznetsov wrote: > > > kernel test robot writes: > > > > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > > > > head: 3b47bc037bd44f142ac09848e8d3ecccc726be99 > > > > commit: a789aeba419647c44d7e7320de20fea037c211d0 KVM: VMX: Rename "vmx/evmcs.{ch}" to "vmx/hyperv.{ch}" > > > > date: 1 year ago > > > > config: x86_64-randconfig-123-20231130 (https://download.01.org/0day-ci/archive/20231130/202311302231.sinLrAig-lkp@intel.com/config) > > > > compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07) > > > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231130/202311302231.sinLrAig-lkp@intel.com/reproduce) > > > > > > > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > > > > the same patch/commit), kindly add following tags > > > > | Reported-by: kernel test robot > > > > | Closes: https://lore.kernel.org/oe-kbuild-all/202311302231.sinLrAig-lkp@intel.com/ > > > > > > > > sparse warnings: (new ones prefixed by >>) > > > > arch/x86/kvm/vmx/hyperv.h:79:30: sparse: sparse: cast truncates bits from constant value (a000a becomes a) > > > > > > This is what ROL16() macro does but the thing is: we actually want to > > > truncate bits by doing an explicit (u16) cast. We can probably replace > > > this with '& 0xffff': > > > > > > #define ROL16(val, n) ((((u16)(val) << (n)) | ((u16)(val) >> (16 - (n)))) & 0xffff) > > > > > > but honestly I don't see much point... > > > > Yeah, just ignore 'em, we get the exact same sparse complaints in vmcs12.c and > > have had great success ignoring those too :-) > > Thanks for the information. We've disabled this warning in the bot to > avoid sending reports against other files with similar code. I would probably recommend keeping the sparse warning enabled, IIRC it does find legitimate bugs from time to time. Or are you able to disable just the ROL16() warning? If so, super cool!