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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3F87FC433E0 for ; Tue, 9 Mar 2021 06:21:42 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B8B776528C for ; Tue, 9 Mar 2021 06:21:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B8B776528C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lists.linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=virtualization-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 6074040163; Tue, 9 Mar 2021 06:21:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id nNYwPBiseAbR; Tue, 9 Mar 2021 06:21:40 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp2.osuosl.org (Postfix) with ESMTP id E7716400E1; Tue, 9 Mar 2021 06:21:39 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id BC34CC000A; Tue, 9 Mar 2021 06:21:39 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 05023C0001 for ; Tue, 9 Mar 2021 06:21:39 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id E6B8749999 for ; Tue, 9 Mar 2021 06:21:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp4.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=suse.com Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qPMtKpZQUCGJ for ; Tue, 9 Mar 2021 06:21:38 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by smtp4.osuosl.org (Postfix) with ESMTPS id DDE82489E0 for ; Tue, 9 Mar 2021 06:21:37 +0000 (UTC) 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=1615270896; 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=auED0x3wS8Wn3FtixUxpL260TFwTyGn7ZjAoR0lab8s=; b=sugliOqHN66fLztniMNHrM6t8IfqY+DtVomXxMlmWAFgzISRB/qAPt21bICd6LaM+SYDMC uBJe4j/rZFNmVWAVk7rUJatk9Q2WH4/0xcdziKE/DPYEFx7uK1b7qiM+BnQ6Sa/iGhifNp pRhpwN8G26dmaykK/TcT+1FJ6NW+vBk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 02BCDAB8C; Tue, 9 Mar 2021 06:21:36 +0000 (UTC) To: Borislav Petkov References: <20210308122844.30488-1-jgross@suse.com> <20210308122844.30488-12-jgross@suse.com> <20210308183058.GC12548@zn.tnic> Subject: Re: [PATCH v5 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE Message-ID: <09410a65-a5dc-db76-d867-f6b0b968323f@suse.com> Date: Tue, 9 Mar 2021 07:21:35 +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: <20210308183058.GC12548@zn.tnic> Cc: "VMware, Inc." , x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , xen-devel@lists.xenproject.org, Thomas Gleixner X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= via Virtualization Reply-To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Content-Type: multipart/mixed; boundary="===============0224467686621224978==" Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --===============0224467686621224978== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qEpMh3Ecfq1JyILFFGFyPlagg1mFokzxT" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --qEpMh3Ecfq1JyILFFGFyPlagg1mFokzxT Content-Type: multipart/mixed; boundary="4WZ1ErrJpnSn17WaCS7ULv4vKLVypghm7"; 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, virtualization@lists.linux-foundation.org, Andy Lutomirski , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Deep Shah , "VMware, Inc." Message-ID: <09410a65-a5dc-db76-d867-f6b0b968323f@suse.com> Subject: Re: [PATCH v5 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE References: <20210308122844.30488-1-jgross@suse.com> <20210308122844.30488-12-jgross@suse.com> <20210308183058.GC12548@zn.tnic> In-Reply-To: <20210308183058.GC12548@zn.tnic> --4WZ1ErrJpnSn17WaCS7ULv4vKLVypghm7 Content-Type: multipart/mixed; boundary="------------518D9DF2B6D10E464777E18C" Content-Language: en-US This is a multi-part message in MIME format. --------------518D9DF2B6D10E464777E18C Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 08.03.21 19:30, Borislav Petkov wrote: > On Mon, Mar 08, 2021 at 01:28:43PM +0100, Juergen Gross wrote: >> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/pa= ravirt.h >> index 36cd71fa097f..04b3067f31b5 100644 >> --- a/arch/x86/include/asm/paravirt.h >> +++ b/arch/x86/include/asm/paravirt.h >> @@ -137,7 +137,8 @@ static inline void write_cr0(unsigned long x) >> =20 >> static inline unsigned long read_cr2(void) >> { >> - return PVOP_CALLEE0(unsigned long, mmu.read_cr2); >> + return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2, >> + "mov %%cr2, %%rax;", ~X86_FEATURE_XENPV); >=20 > Just some cursory poking first - indepth review later. >=20 > Do I see this correctly that the negated feature can be expressed with,= to use > this example here: >=20 > ALTERNATIVE_TERNARY(mmu.read_cr2, X86_FEATURE_XENPV, "", "mov %%cr2, %= %rax;"); >=20 > ? No. This would leave the Xen-pv case with a nop, while we need it to call mmu.read_cr2(). In the Xen-pv case there must be _no_ alternative patching in order to have the paravirt patching do its patching (indirect->direct call). This is exactly the reason why I need to "not feature". The only other solution I can think of would be a "split static_call" handling using ALTERNATIVE_TERNARY(): ALTERNATIVE_TERNARY(initial_static_call(mmu.read_cr2), X86_FEATURE_XENPV, final_static_call(mmu.read_cr2), "mov %%cr2, %%rax;"); with initial_static_call() doing an indirect call, while final_static_call() would do a direct call. Not sure we really want that. 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