From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753904AbcGTQXd (ORCPT ); Wed, 20 Jul 2016 12:23:33 -0400 Received: from mga11.intel.com ([192.55.52.93]:3795 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753814AbcGTQX2 (ORCPT ); Wed, 20 Jul 2016 12:23:28 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,395,1464678000"; d="scan'208";a="737274845" Subject: [PATCH] x86, fpu: do not BUG_ON() in early FPU code To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen Date: Wed, 20 Jul 2016 09:23:28 -0700 Message-Id: <20160720162328.A07B4C4B@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen I don't think it is really possible to have a system where CPUID enumerates support for XSAVE but that it does not have FP/SSE (they are "legacy" features and always present). But, I did manage to hit this case in qemu when I enabled its somewhat shaky XSAVE support. The bummer is that the FPU is set up before we parse the command-line or have *any* console support including earlyprintk. So a BUG() here is worthless. All it does it guarantee that if/when we hit this case we have an empty console. So, remove the BUG() and try to limp along by disabling XSAVE and trying to continue. Signed-off-by: Dave Hansen --- b/arch/x86/kernel/fpu/xstate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN arch/x86/kernel/fpu/xstate.c~x86-fpu-do-not-BUG_ON-early arch/x86/kernel/fpu/xstate.c --- a/arch/x86/kernel/fpu/xstate.c~x86-fpu-do-not-BUG_ON-early 2016-07-20 09:03:07.347941392 -0700 +++ b/arch/x86/kernel/fpu/xstate.c 2016-07-20 09:17:15.001309137 -0700 @@ -715,7 +715,8 @@ void __init fpu__init_system_xstate(void if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask); - BUG(); + fpu__init_disable_system_xstate(); + return; } xfeatures_mask &= fpu__get_supported_xfeatures_mask(); _