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 5BDBAC433FE for ; Wed, 2 Nov 2022 02:47:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230437AbiKBCrl (ORCPT ); Tue, 1 Nov 2022 22:47:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230418AbiKBCrl (ORCPT ); Tue, 1 Nov 2022 22:47:41 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19AC62180D for ; Tue, 1 Nov 2022 19:47:40 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9D10A617A9 for ; Wed, 2 Nov 2022 02:47:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4399CC433D6; Wed, 2 Nov 2022 02:47:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667357259; bh=c5Al9X0yf22zZXheUJCy4tdEcOG/qOUoEDDG9Jhzu6A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZRew/509StWsLwemphFbjYAMu0tpC+DG5fpKQoDdr3rlvP0DQSjTFHkPfKG9I7tMt PaXssIM8ejjhIxIfVcMTN7YkxKUx0HSLqdBFoO3bo5moh9k3az3IxZSDHI6/fWoEGp zAzcEdwSumKuEoISAZzfLdjjk1FPoX3sAC3l3H6g= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Lin X Wang , "Chang S. Bae" , Thomas Gleixner , Sasha Levin Subject: [PATCH 6.0 139/240] x86/fpu: Exclude dynamic states from init_fpstate Date: Wed, 2 Nov 2022 03:31:54 +0100 Message-Id: <20221102022114.521546203@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221102022111.398283374@linuxfoundation.org> References: <20221102022111.398283374@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Chang S. Bae [ Upstream commit a401f45e38754953c9d402f8b3bc965707eecc91 ] == Background == The XSTATE init code initializes all enabled and supported components. Then, the init states are saved in the init_fpstate buffer that is statically allocated in about one page. The AMX TILE_DATA state is large (8KB) but its init state is zero. And the feature comes only with the compacted format with these established dependencies: AMX->XFD->XSAVES. So this state is excludable from init_fpstate. == Problem == But the buffer is formatted to include that large state. Then, this can be the cause of a noisy splat like the below. This came from XRSTORS for the task with init_fpstate in its XSAVE buffer. It is reproducible on AMX systems when the running kernel is built with CONFIG_DEBUG_PAGEALLOC=y and CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y: Bad FPU state detected at restore_fpregs_from_fpstate+0x57/0xd0, reinitializing FPU registers. ... RIP: 0010:restore_fpregs_from_fpstate+0x57/0xd0 ? restore_fpregs_from_fpstate+0x45/0xd0 switch_fpu_return+0x4e/0xe0 exit_to_user_mode_prepare+0x17b/0x1b0 syscall_exit_to_user_mode+0x29/0x40 do_syscall_64+0x67/0x80 ? do_syscall_64+0x67/0x80 ? exc_page_fault+0x86/0x180 entry_SYSCALL_64_after_hwframe+0x63/0xcd == Solution == Adjust init_fpstate to exclude dynamic states. XRSTORS from init_fpstate still initializes those states when their bits are set in the requested-feature bitmap. Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode") Reported-by: Lin X Wang Signed-off-by: Chang S. Bae Signed-off-by: Thomas Gleixner Tested-by: Lin X Wang Link: https://lore.kernel.org/r/20220824191223.1248-4-chang.seok.bae@intel.com Signed-off-by: Sasha Levin --- arch/x86/kernel/fpu/xstate.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index f5ef78633b4c..e77cabfa802f 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -857,9 +857,12 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) update_regset_xstate_info(fpu_user_cfg.max_size, fpu_user_cfg.max_features); - /* Bring init_fpstate size and features up to date */ - init_fpstate.size = fpu_kernel_cfg.max_size; - init_fpstate.xfeatures = fpu_kernel_cfg.max_features; + /* + * init_fpstate excludes dynamic states as they are large but init + * state is zero. + */ + init_fpstate.size = fpu_kernel_cfg.default_size; + init_fpstate.xfeatures = fpu_kernel_cfg.default_features; if (init_fpstate.size > sizeof(init_fpstate.regs)) { pr_warn("x86/fpu: init_fpstate buffer too small (%zu < %d), disabling XSAVE\n", -- 2.35.1