From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754177AbaHKSSg (ORCPT ); Mon, 11 Aug 2014 14:18:36 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:33922 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751506AbaHKSSf (ORCPT ); Mon, 11 Aug 2014 14:18:35 -0400 Message-Id: <1407781112.3399765.151527845.7EC32D9C@webmail.messagingengine.com> X-Sasl-Enc: 53JfYkI73HLkDWipYhy04HdR1o9edeLXm5GLc8WBzqII 1407781112 From: Henrique de Moraes Holschuh To: "H. Peter Anvin" , Borislav Petkov , Fenghua Yu Cc: linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain X-Mailer: MessagingEngine.com Webmail Interface - ajax-e309cf77 In-Reply-To: <53E8D876.1060004@zytor.com> References: <20140809231911.GA4843@khazad-dum.debian.net> <53E8D876.1060004@zytor.com> Subject: Re: BUG: early intel microcode update violating alignment rules Date: Mon, 11 Aug 2014 15:18:32 -0300 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 11, 2014, at 11:51, H. Peter Anvin wrote: > We could put a buffer in the initdata region (we really could use an > initbss region!) or in the brk. That sounds much better than the hideous crap I came up with. The buffer would need to be at least 64KiB in size to be on the safe side. The largest public microcode update ATM is 23KiB. I am not sure if we might need more than 64KiB: the Intel SDM mentions that in real mode the update data must not cross a segment boundary, and also must not exceed a segment limit. I am a bit rusty on real mode, but doesn't that mean, in practice, that microcode update data size is limited in size to 64KiB? -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh