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 1AD4BC77B7A for ; Tue, 13 Jun 2023 05:03:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239900AbjFMFD4 (ORCPT ); Tue, 13 Jun 2023 01:03:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230073AbjFMFDw (ORCPT ); Tue, 13 Jun 2023 01:03:52 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A53368E for ; Mon, 12 Jun 2023 22:03:50 -0700 (PDT) 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 351521FB; Mon, 12 Jun 2023 22:04:35 -0700 (PDT) Received: from [10.162.42.9] (unknown [10.162.42.9]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 41E823F587; Mon, 12 Jun 2023 22:03:47 -0700 (PDT) Message-ID: <77d4d867-cfa1-bdef-dddd-0f28493a4e6e@arm.com> Date: Tue, 13 Jun 2023 10:33:45 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH V3] arm64: Disable EL2 traps for BRBE instructions executed in EL1 Content-Language: en-US To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Mark Brown , Marc Zyngier , linux-kernel@vger.kernel.org References: <20230516083015.569248-1-anshuman.khandual@arm.com> <20230605140038.GB21212@willie-the-truck> From: Anshuman Khandual In-Reply-To: <20230605140038.GB21212@willie-the-truck> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/5/23 19:30, Will Deacon wrote: > On Tue, May 16, 2023 at 02:00:15PM +0530, Anshuman Khandual wrote: >> This disables EL2 traps for BRBE instructions executed in EL1. This would >> enable BRBE to be configured and used successfully in the guest kernel. >> While here, this updates Documentation/arm64/booting.rst as well. > > Is it safe to give the guest access to BRBE if the hypervisor doesn't > switch the state? I'm assuming the architecture defaults to "trap" for a > reason and disabling the trap alone isn't sufficient. Hmm, understood. > > If it _is_ safe, please can you explain that in the commit message? If not, > then this should be at the end of the series adding hypervisor support. Sure, will add the patch when adding hypervisor support for BRBE.