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 E8AD6C32771 for ; Fri, 19 Aug 2022 10:25:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348354AbiHSKY7 (ORCPT ); Fri, 19 Aug 2022 06:24:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348356AbiHSKYx (ORCPT ); Fri, 19 Aug 2022 06:24:53 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E12DCACA1F for ; Fri, 19 Aug 2022 03:24:51 -0700 (PDT) Received: from zn.tnic (p200300ea971b9849329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:971b:9849:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A40851EC064A; Fri, 19 Aug 2022 12:24:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1660904685; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=S0FizUmau6S1/DFtsPjVCVKdQ3LYW9X4CqTGEwR9ThQ=; b=StdfTqkTYWlewpTxDSdX/L4oSdjbKynEMLmaLzQ6nmxy5d3Jgd0XfbLwfLYtsn344gN6R9 HFG0uVBFutcpYfNEEXqK/pP1KBFaeJcWO2nfad9JRg3yb/1uGcIOnDNw+v2hraz5FeBuqS JsEI9vAG2q5FoQP7pAQTUjGUZOfb1yw= Date: Fri, 19 Aug 2022 12:24:41 +0200 From: Borislav Petkov To: Ashok Raj Cc: Thomas Gleixner , Tony Luck , Dave Hansen , LKML Mailing List , X86-kernel , Andy Lutomirski , Tom Lendacky , Jacon Jun Pan Subject: Re: [PATCH v3 1/5] x86/microcode/intel: Check against CPU signature before saving microcode Message-ID: References: <20220817051127.3323755-1-ashok.raj@intel.com> <20220817051127.3323755-2-ashok.raj@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220817051127.3323755-2-ashok.raj@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 17, 2022 at 05:11:23AM +0000, Ashok Raj wrote: > When save_microcode_patch() is looking to replace an existing microcode in > the cache, current code is *only* checks the CPU sig/pf in the main Write those "sig/pf" things out once so that it is clear what that is. > header. Microcode can carry additional sig/pf combinations in the extended > signature table, which is completely missed today. > > For e.g. Current patch is a multi-stepping patch and new incoming patch is > a specific patch just for this CPUs stepping. > > patch1: > fms3 <--- header FMS > ... > ext_sig: > fms1 > fms2 > > patch2: new > fms2 <--- header FMS > > Current code takes only fms3 and checks with patch2 fms2. So, find_matching_signature() does all the signatures matching and scanning already. If anything, that function should tell its callers whether the patch it is looking at - the fms2 one - should replace the current one or not. I.e., all the logic to say how strong a patch match is, should be concentrated there. And then the caller will do the according action. > saved_patch.header.fms3 != new_patch.header.fms2, so save_microcode_patch > saves it to the end of list instead of replacing patch1 with patch2. > > There is no functional user observable issue since find_patch() skips > patch versions that are <= current_patch and will land on patch2 properly. > > Nevertheless this will just end up storing every patch that isn't required. > Kernel just needs to store the latest patch. Otherwise its a memory leak > that sits in kernel and never used. Oh well. > Cc: stable@vger.kernel.org Why? This looks like a small correction to me which doesn't need to go to stable... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette