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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7505C4360F for ; Thu, 21 Feb 2019 13:37:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7C9E2084F for ; Thu, 21 Feb 2019 13:37:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="sKTb2zMH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727128AbfBUNhx (ORCPT ); Thu, 21 Feb 2019 08:37:53 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:45754 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725385AbfBUNhx (ORCPT ); Thu, 21 Feb 2019 08:37:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=NpcwRPiUBsDTC6WNdOOEbdvIamRDbsI3Cs5FT6037R8=; b=sKTb2zMH+dfxctWPPWpR688XG mqopdVXZ9O38IK/NurCTVcomtPrLltsxwM2s0Fovr/Ma4AxUi9BiufcItxFOh+IAzCmTJ4e9BD5MT i/9lTb/y9pltS6JU7kirEYzWlIFlicaBi8F49ifSSR9mgfnpHt5hT9IgiE4BUTGa4gTmaQLfFmCBh esWCHGuM/g81Y4yMwBLzINqQ+5iOL2eD/91svq7i8ICFUtd93V6xqVIcAsWdSeWP1sAlYBm7JwEL7 2ReQbGlADfasbSi1gRZ4WAsoBCpV9EJjMILQR5syTAJbvQ9KlFNwP0rvGrnowcSGa1AVJxwonIf+I UhaHhHZEg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gwoXr-00015i-Cm; Thu, 21 Feb 2019 13:37:47 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id CADF92030EE5E; Thu, 21 Feb 2019 14:37:45 +0100 (CET) Date: Thu, 21 Feb 2019 14:37:45 +0100 From: Peter Zijlstra To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Andi Kleen , x86@kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH] x86/fpu: Parse comma separated list passed in clearcpuid Message-ID: <20190221133745.GP32494@hirez.programming.kicks-ass.net> References: <20190221131225.22063-1-prarit@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190221131225.22063-1-prarit@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 21, 2019 at 08:12:25AM -0500, Prarit Bhargava wrote: > Users cannot disable multiple CPU features with the kernel parameter > clearcpuid=. For example, "clearcpuid=154 clearcpuid=227" only disables > CPUID bit 154. > > Previous to commit 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE > argument") it was possible to pass multiple clearcpuid options as kernel > parameters using individual entries. With the new code it isn't easy to > replicate exactly that behaviour but a comma separated list can be easily > implemented, eg) "clearcpuid=154,227" > > Make the clearcpuid parse a comma-separated list of values instead of only > a single value. So I think the feature is broken as is; because it doesn't clear the CPUID bits for userspace. something along the lines of: https://lkml.kernel.org/r/20190212164833.GK32494@hirez.programming.kicks-ass.net would be required to make it so.