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=-17.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 4AB65C07E9E for ; Sat, 10 Jul 2021 13:09:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32E94613E3 for ; Sat, 10 Jul 2021 13:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232478AbhGJNMY (ORCPT ); Sat, 10 Jul 2021 09:12:24 -0400 Received: from mga03.intel.com ([134.134.136.65]:52358 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231458AbhGJNL4 (ORCPT ); Sat, 10 Jul 2021 09:11:56 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10040"; a="209867330" X-IronPort-AV: E=Sophos;i="5.84,229,1620716400"; d="scan'208";a="209867330" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2021 06:09:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.84,229,1620716400"; d="scan'208";a="488742416" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by FMSMGA003.fm.intel.com with ESMTP; 10 Jul 2021 06:09:09 -0700 From: "Chang S. Bae" To: bp@suse.de, luto@kernel.org, tglx@linutronix.de, mingo@kernel.org, x86@kernel.org Cc: len.brown@intel.com, dave.hansen@intel.com, thiago.macieira@intel.com, jing2.liu@intel.com, ravi.v.shankar@intel.com, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v7 22/26] x86/fpu/xstate: Skip writing zeros to signal frame for dynamic user states if in INIT-state Date: Sat, 10 Jul 2021 06:03:09 -0700 Message-Id: <20210710130313.5072-23-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210710130313.5072-1-chang.seok.bae@intel.com> References: <20210710130313.5072-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org By default, for XSTATE features in the INIT-state, XSAVE writes zeros to the uncompressed destination buffer. E.g., if you are not using AVX-512, you will still get a bunch of zeros on the signal stack where live AVX-512 data would go. For 'dynamic user state' (currently only XTILEDATA), explicitly skip this data transfer. The result is that the user buffer for the AMX region will not be touched by XSAVE. [ Reading XINUSE takes about 20-30 cycles, but writing zeros consumes about 5-times or more, e.g., for XTILEDATA. ] Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v5: * Mentioned the optimization trade-offs in the changelog. (Dave Hansen) * Added code comment. Changes from v4: * Added as a new patch. --- arch/x86/include/asm/fpu/internal.h | 38 +++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index a1ccef6d4520..c9f1573f3ff8 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -337,8 +337,9 @@ static inline void os_xrstor(struct xregs_state *xstate, u64 mask) */ static inline int xsave_to_user_sigframe(struct xregs_state __user *buf) { + struct fpu *fpu = ¤t->thread.fpu; u32 lmask, hmask; - u64 mask; + u64 state_mask; int err; /* @@ -346,21 +347,38 @@ static inline int xsave_to_user_sigframe(struct xregs_state __user *buf) * internally, e.g. PKRU. That's user space ABI and also required * to allow the signal handler to modify PKRU. */ - mask = xfeatures_mask_uabi(); + state_mask = xfeatures_mask_uabi(); + + if (!xfeatures_mask_user_dynamic) + goto mask_ready; /* * Exclude dynamic user states for non-opt-in threads. */ - if (xfeatures_mask_user_dynamic) { - struct fpu *fpu = ¤t->thread.fpu; - - mask &= fpu->dynamic_state_perm ? - fpu->state_mask : - ~xfeatures_mask_user_dynamic; + if (!fpu->dynamic_state_perm) { + state_mask &= ~xfeatures_mask_user_dynamic; + } else { + u64 dynamic_state_mask; + + state_mask &= fpu->state_mask; + + dynamic_state_mask = state_mask & xfeatures_mask_user_dynamic; + if (dynamic_state_mask && boot_cpu_has(X86_FEATURE_XGETBV1)) { + u64 dynamic_xinuse, dynamic_init; + u64 xinuse = xgetbv(1); + + dynamic_xinuse = xinuse & dynamic_state_mask; + dynamic_init = ~xinuse & dynamic_state_mask; + if (dynamic_init) { + state_mask &= ~xfeatures_mask_user_dynamic; + state_mask |= dynamic_xinuse; + } + } } - lmask = mask; - hmask = mask >> 32; +mask_ready: + lmask = state_mask; + hmask = state_mask >> 32; /* * Clear the xsave header first, so that reserved fields are -- 2.17.1