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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 9636EC43142 for ; Mon, 25 Jun 2018 16:01:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5913225DA1 for ; Mon, 25 Jun 2018 16:01:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5913225DA1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ACULAB.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 S1755316AbeFYQBK convert rfc822-to-8bit (ORCPT ); Mon, 25 Jun 2018 12:01:10 -0400 Received: from smtp-out4.electric.net ([192.162.216.184]:56007 "EHLO smtp-out4.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754716AbeFYQBH (ORCPT ); Mon, 25 Jun 2018 12:01:07 -0400 Received: from 1fXTvJ-0001Gf-V3 by out4d.electric.net with emc1-ok (Exim 4.90_1) (envelope-from ) id 1fXTvM-0001hf-T6; Mon, 25 Jun 2018 09:01:04 -0700 Received: by emcmailer; Mon, 25 Jun 2018 09:01:04 -0700 Received: from [156.67.243.126] (helo=AcuMS.aculab.com) by out4d.electric.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1fXTvJ-0001Gf-V3; Mon, 25 Jun 2018 09:01:01 -0700 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 25 Jun 2018 17:02:40 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 25 Jun 2018 17:02:40 +0100 From: David Laight To: 'Matthias Kaehlcke' , Paolo Bonzini , =?iso-8859-2?Q?Radim_Kr=E8m=E1=F8?= , Thomas Gleixner , "H . Peter Anvin" CC: "x86@kernel.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Nick Desaulniers , Joe Perches Subject: RE: [PATCH v2] kvm: x86: mmu: Add cast to negated bitmasks in update_permission_bitmask() Thread-Topic: [PATCH v2] kvm: x86: mmu: Add cast to negated bitmasks in update_permission_bitmask() Thread-Index: AQHUCAN80F3SBShFI0K/KXIEJhRI5KRxK3VA Date: Mon, 25 Jun 2018 16:02:40 +0000 Message-ID: References: <20180619192504.180479-1-mka@chromium.org> In-Reply-To: <20180619192504.180479-1-mka@chromium.org> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.33] Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Outbound-IP: 156.67.243.126 X-Env-From: David.Laight@ACULAB.COM X-Proto: esmtps X-Revdns: X-HELO: AcuMS.aculab.com X-TLS: TLSv1.2:ECDHE-RSA-AES256-SHA384:256 X-Authenticated_ID: X-PolicySMART: 3396946, 3397078 X-Virus-Status: Scanned by VirusSMART (c) X-Virus-Status: Scanned by VirusSMART (s) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Matthias Kaehlcke > Sent: 19 June 2018 20:25 > To: Paolo Bonzini; Radim Krèmáø; Thomas Gleixner; H . Peter Anvin > Cc: x86@kernel.org; kvm@vger.kernel.org; linux-kernel@vger.kernel.org; Nick Desaulniers; Joe Perches; > Matthias Kaehlcke > Subject: [PATCH v2] kvm: x86: mmu: Add cast to negated bitmasks in update_permission_bitmask() > > update_permission_bitmask() negates u8 bitmask values and assigns them > to variables of type u8. Since the MSB is set in the bitmask values the > compiler expands the negated values to int, which then is assigned to > an u8 variable. Cast the negated value back to u8. > > This fixes several warnings like this when building with clang: > > arch/x86/kvm/mmu.c:4266:39: error: implicit conversion from 'int' to 'u8' > (aka 'unsigned char') changes value from -205 to 51 [-Werror, > -Wconstant-conversion] > u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0; > ~~ ^~ Shoot the compiler writer - or turn off that warning. Or try 'w ^ 0xff'. David