Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935674AbcCQNOJ (ORCPT ); Thu, 17 Mar 2016 09:14:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54633 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbcCQNOH (ORCPT ); Thu, 17 Mar 2016 09:14:07 -0400 Subject: Re: [PATCH v2] firmware: qemu_fw_cfg.c: hold ACPI global lock during device access To: "Michael S. Tsirkin" , Gabriel Somlo References: <20160308183050.GJ2049@HEDWIG.INI.CMU.EDU> <20160316185440-mutt-send-email-mst@redhat.com> Cc: Greg KH , robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, arnd@arndb.de, lersek@redhat.com, ralf@linux-mips.org, rmk+kernel@arm.linux.org.uk, eric@anholt.net, hanjun.guo@linaro.org, zajec5@gmail.com, sudeep.holla@arm.com, agross@codeaurora.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, qemu-devel@nongnu.org, imammedo@redhat.com, peter.maydell@linaro.org, leif.lindholm@linaro.org, ard.biesheuvel@linaro.org, kraxel@redhat.com, ehabkost@redhat.com, luto@amacapital.net, stefanha@gmail.com, revol@free.fr, matt@codeblueprint.co.uk, rth@twiddle.net From: Paolo Bonzini Message-ID: <56EAAD92.10007@redhat.com> Date: Thu, 17 Mar 2016 14:13:54 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160316185440-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 17 Mar 2016 13:14:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 914 Lines: 27 On 16/03/2016 17:57, Michael S. Tsirkin wrote: > On Tue, Mar 08, 2016 at 01:30:50PM -0500, Gabriel Somlo wrote: >> Allowing for the future possibility of implementing AML-based >> (i.e., firmware-triggered) access to the QEMU fw_cfg device, >> acquire the global ACPI lock when accessing the device on behalf >> of the guest-side sysfs driver, to prevent any potential race >> conditions. >> >> Suggested-by: Michael S. Tsirkin >> Signed-off-by: Gabriel Somlo > > So this patch makes sense of course. > > > Given the recent discussion on QEMU mailing list, > I think there is an additional patch that we need: > filter the files exposed to userspace by "opt/" prefix. > > This will ensure that we can change all other fw cfg files > at will without breaking guest scripts. That makes no sense, all other fw_cfg files are firmware ABI so we cannot change them anyway. Paolo