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 7807CC61DA4 for ; Thu, 9 Feb 2023 15:16:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231334AbjBIPQG (ORCPT ); Thu, 9 Feb 2023 10:16:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56262 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231342AbjBIPPf (ORCPT ); Thu, 9 Feb 2023 10:15:35 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 387F86310C for ; Thu, 9 Feb 2023 07:15:03 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E6DAE2F4; Thu, 9 Feb 2023 07:15:43 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.89.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B9F493F703; Thu, 9 Feb 2023 07:14:59 -0800 (PST) Date: Thu, 9 Feb 2023 15:13:06 +0000 From: Mark Rutland To: Ard Biesheuvel Cc: Will Deacon , linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Catalin Marinas , Kees Cook , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen Subject: Re: [PATCH v2 2/3] efi: arm64: Wire up BTI annotation in memory attributes table Message-ID: References: <20230206124938.272988-1-ardb@kernel.org> <20230206124938.272988-3-ardb@kernel.org> <20230208130007.GA13529@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Thu, Feb 09, 2023 at 03:21:55PM +0100, Ard Biesheuvel wrote: > On Wed, 8 Feb 2023 at 15:36, Ard Biesheuvel wrote: > > On Wed, 8 Feb 2023 at 15:25, Mark Rutland wrote: > > > I believe that there's no issue with mismatched CPUs, but there *might* might > > > be a different issue with the ordering of feature detection and usage of the > > > cap: > > > > > > * If CONFIG_ARM64_BTI_KERNEL=y, then the ARM64_BTI cap is detected as a strict > > > boot cpu feature, and secondaries without it will be rejected. > > > > > > * If CONFIG_ARM64_BTI_KERNEL=n then the ARM64_BTI cap is detected as a system > > > feature, and so we only set the cap bit after bringing all secondary CPUs > > > online, and only when *all* CPUs support it. > > > > > > The happens under setup_cpu_features(), called from smp_cpus_done(). > > > > > > So there's no issue with mismatch, but if system_supports_bti is called before > > > smp_cpus_done() on a CONFIG_ARM64_BTI_KERNEL kernel it will return false. When > > > do we set up the EFI mappings relative to that? > > > > > > > Currently it is an early initcall so before SMP, but that is not > > really necessary - the EFI table that carries this annotation is an > > overlay that could easily be applied later. > > > > OTOH, what is the penalty for setting the GP attribute and using the > > translation table on a core that does not implement BTI? > > I'll merge this with the CONFIG_ARM64_BTI_KERNEL check re-added, if > nobody minds? That make sense to me; with the CONFIG_ARM64_BTI_KERNEL check: Acked-by: Mark Rutland Mark.