From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754941AbbDJUl1 (ORCPT ); Fri, 10 Apr 2015 16:41:27 -0400 Received: from mga11.intel.com ([192.55.52.93]:53073 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751967AbbDJUlZ (ORCPT ); Fri, 10 Apr 2015 16:41:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,558,1422950400"; d="scan'208";a="554298219" Date: Fri, 10 Apr 2015 13:41:25 -0700 From: Andi Kleen To: Andy Lutomirski Cc: Andi Kleen , X86 ML , Andrew Lutomirski , "linux-kernel@vger.kernel.org" , Steven Rostedt , Borislav Petkov Subject: Re: [PATCH 4/8] x86: Add support for rd/wr fs/gs base Message-ID: <20150410204125.GS15335@tassilo.jf.intel.com> References: <1428681033-1549-1-git-send-email-andi@firstfloor.org> <1428681033-1549-5-git-send-email-andi@firstfloor.org> <20150410202132.GQ15335@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > It wouldn't take any additional memory at all. Currently we have 8k > of "debug" stack which is really two 4k pieces, and you're putting the > kernel gs base in the bottom word. I'm suggesting that you duplicate > the kernel gs base at the bottom work and the bottom word + 4k. We > already have a hard limit of 4k of debug stack because of the IST > shift mechanism -- it really is two separate 4k stacks, not one 8k > stack. Seems like a hack. What happens if we add an uneven number of stacks? Just handling it in the code is simple enough. -Andi -- ak@linux.intel.com -- Speaking for myself only