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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 4D5A0C433E0 for ; Wed, 10 Mar 2021 07:53:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19E4C64FC4 for ; Wed, 10 Mar 2021 07:53:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232246AbhCJHwy (ORCPT ); Wed, 10 Mar 2021 02:52:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:59846 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232395AbhCJHwm (ORCPT ); Wed, 10 Mar 2021 02:52:42 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1615362761; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fmagm0g6SG9wOn5qY9NDsKJhRGoqp/JA1hP32sWV3T4=; b=VyZrbZQKMeSMXCTWCSyz0CqR7B2gWSK3gyj6vBitCnWoQi7styoaQILCubHOquaJugUypv ovDZFEds58x63Nt44akxgZiZ4BSosHqqH92NNeihDJ/FNj5MIk3ysmnm9p42v5UM3/fAEh IKGW1y8bpuZ2EbURSOq7bZEdO9hkQPE= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E5E6DAE44; Wed, 10 Mar 2021 07:52:40 +0000 (UTC) Subject: Re: [PATCH v6 04/12] x86/alternative: support not-feature To: Borislav Petkov Cc: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" References: <20210309134813.23912-1-jgross@suse.com> <20210309134813.23912-5-jgross@suse.com> <20210310060705.GB23521@zn.tnic> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <1b95376a-56e1-ab3e-aa85-73a9d38aaaf7@suse.com> Date: Wed, 10 Mar 2021 08:52:40 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210310060705.GB23521@zn.tnic> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="dTWXoiEr2CUu22HQ0ZizVBKitnbXxMRRZ" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --dTWXoiEr2CUu22HQ0ZizVBKitnbXxMRRZ Content-Type: multipart/mixed; boundary="p5M5sLIHJQkn6BTbMQSaAVowf7JqkAJIS"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Borislav Petkov Cc: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Message-ID: <1b95376a-56e1-ab3e-aa85-73a9d38aaaf7@suse.com> Subject: Re: [PATCH v6 04/12] x86/alternative: support not-feature References: <20210309134813.23912-1-jgross@suse.com> <20210309134813.23912-5-jgross@suse.com> <20210310060705.GB23521@zn.tnic> In-Reply-To: <20210310060705.GB23521@zn.tnic> --p5M5sLIHJQkn6BTbMQSaAVowf7JqkAJIS Content-Type: multipart/mixed; boundary="------------67B61F63DAEE5E8820EB9FAE" Content-Language: en-US This is a multi-part message in MIME format. --------------67B61F63DAEE5E8820EB9FAE Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 10.03.21 07:07, Borislav Petkov wrote: > On Tue, Mar 09, 2021 at 02:48:05PM +0100, Juergen Gross wrote: >> Add support for alternative patching for the case a feature is not >> present on the current cpu. >> >> For users of ALTERNATIVE() and friends an inverted feature is specifie= d >> by applying the ALT_NOT() macro to it, e.g.: >> >> ALTERNATIVE(old, new, ALT_NOT(feature)) >> >> Signed-off-by: Juergen Gross >> --- >> V5: >> - split off from next patch >> - reworked to use flag byte (Boris Petkov) >> V6: >> - rework again to not use flag byte (Boris Petkov) >> --- >> arch/x86/include/asm/alternative-asm.h | 3 +++ >> arch/x86/include/asm/alternative.h | 3 +++ >> arch/x86/kernel/alternative.c | 19 ++++++++++++++----- >> 3 files changed, 20 insertions(+), 5 deletions(-) >=20 > LGTM, minor touchups I'd do ontop: >=20 > --- >=20 > diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/= alternative.h > index 89889618ae01..fd205cdcfbad 100644 > --- a/arch/x86/include/asm/alternative.h > +++ b/arch/x86/include/asm/alternative.h > @@ -55,18 +55,18 @@ > ".long 999b - .\n\t" \ > ".popsection\n\t" > =20 > +#define ALTINSTR_FLAG_INV (1 << 15) > +#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV) > + > struct alt_instr { > s32 instr_offset; /* original instruction */ > s32 repl_offset; /* offset to replacement instruction */ > u16 cpuid; /* cpuid bit set for replacement */ > -#define ALTINSTR_FLAG_INV (1 << 15) > u8 instrlen; /* length of original instruction */ > u8 replacementlen; /* length of new instruction */ > u8 padlen; /* length of build-time padding */ > } __packed; > =20 > -#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV) > - Did you look at patch 13? :-) > /* > * Debug flag that can be tested to see whether alternative > * instructions were patched in already: > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternativ= e.c > index d8e669a1546f..133b549dc091 100644 > --- a/arch/x86/kernel/alternative.c > +++ b/arch/x86/kernel/alternative.c > @@ -397,9 +397,10 @@ void __init_or_module noinline apply_alternatives(= struct alt_instr *start, > BUG_ON(feature >=3D (NCAPINTS + NBUGINTS) * 32); > =20 > /* > - * Drop out if either: > - * - feature not available, but required, or > - * - feature available, but NOT required > + * Patch if either: > + * - feature is present > + * - feature not present but ALTINSTR_FLAG_INV is set to mean, > + * patch if feature is *NOT* present. Okay. 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