Received: by 2002:a05:6358:3188:b0:123:57c1:9b43 with SMTP id q8csp2507832rwd; Fri, 9 Jun 2023 12:17:23 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6AaMq1bqr6G5Yu4RrRCpBM/ntWQ9VpUlrbQvj33XkdZSfySFKhBbQCF74WPD/HE9NjQaJJ X-Received: by 2002:a05:6a20:970f:b0:105:f8e4:7214 with SMTP id hr15-20020a056a20970f00b00105f8e47214mr1908300pzc.42.1686338242883; Fri, 09 Jun 2023 12:17:22 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1686338242; cv=none; d=google.com; s=arc-20160816; b=C/fbz0/UhM6lfIWbZeMisIpBZQjyT1KrnygsrHfDwknJhKFS5nvEoYI+g/4+dT4L7F 1FHvDqvub79b9IfEVJNA26cgfsNrpYl8Qmy3gQGgMfa3oagBgrAUak15OgNATJ+bNOu2 XUpytsfe8r91P6IV2nRHtv9cAJYt3k33R1pxTMlpg2VGx3Ee40vz1D3DoorkYqKOtgpp N9gGiseHgdRyM6Jw/r/boIFbMlXcRHtM+J0SwVbeTfIA4M5CKeTk1Wll37xH3g2o5m5N rci/VOxbFehUEThsKS3XsjrnTj8vLDxI9yV2KmPcztqt3lFWVYrn+y9G5Bca2brlxwWl sRdA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=kFAT63F3rOigITJwOF0BR5aoRwU2ve+uCaRoniXJg+w=; b=epkz9E2drJbPSkhL2TbVuBENIvkYFAyIcqKLv0Cyj4KOP4B61HCGL1In+b4TRycCYE d2UVHAaZVnNnscHACKs7f501D4oXtzbvt9Zmm8ibfVfxTqfLutmtYv+/qPbC5xxv1qws ET2Wx6kKwq5qFeUd8XEJ95u5VwkpG1S6aSZvwaKZgWBMjXqk7jV+eNjJb5o54HFzITO/ OZExakLVqIs5QcFqUuPuQKbvWGuc6aJ5UIstGKt0nid/R9r7+Z8NPH5G0zDUsNIbiPJl 8pdep4RilL+f1dNyVgmIGTscSyzHQapvxrtUSTxrA6/eUT86iIYPo531rMZX+M805mai uBmw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=jqZausiQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Return-Path: Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id k11-20020a637b4b000000b00543f6a35a43si3143170pgn.306.2023.06.09.12.16.51; Fri, 09 Jun 2023 12:17:22 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=jqZausiQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232142AbjFISiJ (ORCPT + 99 others); Fri, 9 Jun 2023 14:38:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230454AbjFIShq (ORCPT ); Fri, 9 Jun 2023 14:37:46 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2800B4231 for ; Fri, 9 Jun 2023 11:37:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1686335845; x=1717871845; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=G6sE0O+Ymn27nVkvLirQB/p1cOObowjit5BY1oI6ToA=; b=jqZausiQqiliZT/hXqP1O+IG1QdCGRCqzgWrrEe8TEy8Sl5kfHOYsi6g 4T+cUj4RkdnHs0PHC4uBbqTqZcNwApAJ9iXcSClMslTgXCSzobp/X2WQD iXWFSiHYcLAL+qNN1rH2lgAmJ8v41nqlv1wDS6Om4nNxdIjLvTTLe0Ofq YGDainiuXsUl/Ll4ort/wPu0Ja7QIvHCXXhYfoJn6vhDUVFqwEAC3SGQP 92I7bLghifsegjkT0c+96uXLNAkL/cNvPHNrR8+hyanKej7GpDKEqWP19 JjT0WQKPh33RQsiP0o1uMtM+GUOWhxE1ih3SMBwFX9Xsxhp8Y+UM1HJLn w==; X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="338022207" X-IronPort-AV: E=Sophos;i="6.00,230,1681196400"; d="scan'208";a="338022207" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jun 2023 11:37:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10736"; a="710444098" X-IronPort-AV: E=Sophos;i="6.00,230,1681196400"; d="scan'208";a="710444098" Received: from black.fi.intel.com (HELO black.fi.intel.com.) ([10.237.72.28]) by orsmga002.jf.intel.com with ESMTP; 09 Jun 2023 11:37:17 -0700 From: Alexander Shishkin To: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Dave Hansen , Ravi Shankar , Tony Luck , Sohil Mehta Cc: Alexander Shishkin , Dave Hansen Subject: [PATCH v3 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Date: Fri, 9 Jun 2023 21:36:30 +0300 Message-Id: <20230609183632.48706-11-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230609183632.48706-1-alexander.shishkin@linux.intel.com> References: <20230609183632.48706-1-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since EMULATE mode of vsyscall disables LASS, because fixing the LASS violations during the EMULATE mode would need complex instruction decoding, document this fact in kernel-parameters.txt. Cc: Andy Lutomirski Suggested-by: Dave Hansen Signed-off-by: Alexander Shishkin --- Documentation/admin-guide/kernel-parameters.txt | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9e5bab29685f..efed9193107e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6850,7 +6850,9 @@ emulate Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall page is - readable. + readable. This also disables the LASS + feature to allow userspace to poke around + the vsyscall page. xonly [default] Vsyscalls turn into traps and are emulated reasonably safely. The vsyscall -- 2.39.2