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 393AFC43334 for ; Wed, 29 Jun 2022 22:51:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230222AbiF2Wvv (ORCPT ); Wed, 29 Jun 2022 18:51:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229539AbiF2Wvs (ORCPT ); Wed, 29 Jun 2022 18:51:48 -0400 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A81BD1CB07; Wed, 29 Jun 2022 15:51:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1656543107; x=1688079107; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=pPUlqKZCesuVnLqny3F3F4siQYTkDVZUwF5WOXqskQw=; b=WMA3xoHkj8nC5etQKVy7SsSFxdf8emIIM+n47ikaY7T5SX8ubK0TjjaT edOlj3Cvj/Pkyur00oFNea3PpKlvQiYYWtpMfEpWdTb2V2shFwNmOL9lm 66/8hAU5g4ZlvkIVaOfphfLKzZ9Lyk8MxRCk8SUSg6u/FPH9ttSmXp3ZT YD95Rd20Hy/QkE7NyTX13sydzo0ob5KJANoNrKnZb8Nq2yiuv+gXNAPQW /zst6IPbLaBVXYNRVB6ynTse9NwjdXRiKpZDfkZg1vlN9/wSnqpj0ByTB i3wdYHxmWVb+UPIw8lFBoZyuVfg9SgxEL1ZuBMGQ1YzuW7DL38YRBgJHg Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10393"; a="343871875" X-IronPort-AV: E=Sophos;i="5.92,232,1650956400"; d="scan'208";a="343871875" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2022 15:51:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,232,1650956400"; d="scan'208";a="917795907" Received: from chang-linux-3.sc.intel.com ([172.25.66.173]) by fmsmga005.fm.intel.com with ESMTP; 29 Jun 2022 15:51:46 -0700 From: "Chang S. Bae" To: dave.hansen@intel.com, len.brown@intel.com, tony.luck@intel.com, rafael.j.wysocki@intel.com, reinette.chatre@intel.com, dan.j.williams@intel.com Cc: corbet@lwn.net, linux-doc@vger.kernel.org, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v2 1/1] Documentation/x86: Add the AMX enabling example Date: Wed, 29 Jun 2022 15:42:35 -0700 Message-Id: <20220629224235.20589-2-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220629224235.20589-1-chang.seok.bae@intel.com> References: <20220629224235.20589-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Explain steps to enable the dynamic feature with a code example. Signed-off-by: Chang S. Bae Reviewed-by: Thiago Macieira Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v1: * Update the description without mentioning CPUID & XGETBV (Dave Hansen). --- Documentation/x86/xstate.rst | 42 ++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/Documentation/x86/xstate.rst b/Documentation/x86/xstate.rst index 5cec7fb558d6..c439901419fb 100644 --- a/Documentation/x86/xstate.rst +++ b/Documentation/x86/xstate.rst @@ -64,6 +64,48 @@ the handler allocates a larger xstate buffer for the task so the large state can be context switched. In the unlikely cases that the allocation fails, the kernel sends SIGSEGV. +AMX TILE_DATA enabling example +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The following steps dynamically enable TILE_DATA: + + 1. An application first needs to determine the feature support:: + + #include + #include + #include + #include + + #define ARCH_GET_XCOMP_SUPP 0x1021 + + #define XFEATURE_XTILECFG 17 + #define XFEATURE_XTILEDATA 18 + #define XFEATURE_MASK_XTILE ((1 << XFEATURE_XTILECFG) | (1 << XFEATURE_XTILEDATA)) + + unsigned long features; + long rc; + + ... + + rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_SUPP, &features); + + if (!rc && (features & XFEATURE_MASK_XTILE) == XFEATURE_MASK_XTILE) + printf("AMX is available.\n"); + + 2. After determining support for AMX, an application must explicitly ask + permission to use it:: + + #define ARCH_REQ_XCOMP_PERM 0x1023 + + ... + + rc = syscall(SYS_arch_prctl, ARCH_REQ_XCOMP_PERM, XFEATURE_XTILEDATA); + + if (!rc) + printf("AMX is ready for use.\n"); + +Note this example does not include the sigaltstack preparation. + Dynamic features in signal frames --------------------------------- -- 2.17.1