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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7F37ECAAD5 for ; Fri, 9 Sep 2022 20:26:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232306AbiIIU0e (ORCPT ); Fri, 9 Sep 2022 16:26:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231342AbiIIU0M (ORCPT ); Fri, 9 Sep 2022 16:26:12 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0EE2F6B8D; Fri, 9 Sep 2022 13:25:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662755138; x=1694291138; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=ZjDsoVe/m26NmdDU80Jql+Vu5NT9QFMQwUPtL9OGYPw=; b=E5sxz112FhR+H+MAqzCMy4LbDtZl2pzraWAAWsnVJncJZufkSIXLojxP m4NlWsSDK06yJD+m8d4U0DDBH56K60UKOT1hknEYWvcGLDinh/79JdsmL F6EfIqs1403A/yMC74fIb+2M5SvDZLCeswkRZ3Pu46Q34tYwBJz9MRvJk jLJO7M0HwQxhvRsYLl5vD1mxyO7IKOnONXyo1oXI74mBl2pdO3uNasU5T uDjt4BcKwpE3VxP4NoOXXYWZHu7fyTpDuyyzGObniHTcFQCz9mL/8Kann ClbROca8v0cj114Yy/A2FNViuQUiLUKUd6TmWqG5DTs+MGmHI8axMsq7m g==; X-IronPort-AV: E=McAfee;i="6500,9779,10465"; a="280584699" X-IronPort-AV: E=Sophos;i="5.93,304,1654585200"; d="scan'208";a="280584699" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2022 13:25:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,304,1654585200"; d="scan'208";a="611162993" Received: from chang-linux-3.sc.intel.com ([172.25.66.173]) by orsmga007.jf.intel.com with ESMTP; 09 Sep 2022 13:25:35 -0700 From: "Chang S. Bae" To: x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com Cc: hpa@zytor.com, corbet@lwn.net, bagasdotme@gmail.com, tony.luck@intel.com, yang.zhong@intel.com, linux-doc@vger.kernel.org, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v4 1/4] Documentation/x86: Explain the purpose for dynamic features Date: Fri, 9 Sep 2022 13:15:37 -0700 Message-Id: <20220909201540.17705-2-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220909201540.17705-1-chang.seok.bae@intel.com> References: <20220909201540.17705-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org This summary will help to guide the proper use of the enabling model. Signed-off-by: Chang S. Bae Reviewed-by: Tony Luck Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org --- Changes from v3: * Add as a new patch (Tony Luck). --- Documentation/x86/xstate.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/x86/xstate.rst b/Documentation/x86/xstate.rst index 5cec7fb558d6..2577b28ad942 100644 --- a/Documentation/x86/xstate.rst +++ b/Documentation/x86/xstate.rst @@ -11,6 +11,20 @@ are enabled by XCR0 as well, but the first use of related instruction is trapped by the kernel because by default the required large XSTATE buffers are not allocated automatically. +The purpose for dynamic features +-------------------------------- + + - Legacy userspace libraries have hard-coded sizes for an alternate signal + stack. With the arch_prctl() options, the signal frame beyond AVX-512 + and PKRU will not be written by old programs as they are prevented from + using dynamic features. Then, the small signal stack will be compatible + on systems that support dynamic features. + + - Modern server systems are consolidating more applications to share the + CPU resource. The risk of applications interfering with each other is + growing. The controllability on the resource trends to be more + warranted. Thus, this permission mechanism will be useful for that. + Using dynamically enabled XSTATE features in user space applications -------------------------------------------------------------------- -- 2.17.1