From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 05E5A211D07A9 for ; Fri, 1 Mar 2019 07:27:25 -0800 (PST) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 11BED34451E; Fri, 1 Mar 2019 15:27:22 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-56.rdu2.redhat.com [10.10.120.56]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0A71D60BEE; Fri, 1 Mar 2019 15:27:18 +0000 (UTC) To: Ard Biesheuvel , Heyi Guo Cc: "edk2-devel@lists.01.org" , wanghaibin 00208455 , Jian J Wang , Hao Wu , Julien Grall , Peter Maydell References: <1551341112-21645-1-git-send-email-guoheyi@huawei.com> From: Laszlo Ersek Message-ID: Date: Fri, 1 Mar 2019 16:27:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 01 Mar 2019 15:27:22 +0000 (UTC) Subject: Re: [RFC 0/3] Enable runtime serial debug for ArmVirtQemu X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Mar 2019 15:27:26 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit +Peter, for the last few paragraphs On 02/28/19 13:10, Ard Biesheuvel wrote: > On Thu, 28 Feb 2019 at 09:06, Heyi Guo wrote: >> >> Serial port output is useful when debugging UEFI runtime services in OS runtime. >> The patches are trying to provide a handy method to enable runtime serial port >> debug for ArmVirtQemu. >> >> Cc: Jian J Wang >> Cc: Hao Wu >> Cc: Laszlo Ersek >> Cc: Ard Biesheuvel >> Cc: Julien Grall >> >> Heyi Guo (3): >> MdeModulePkg/StatusCode: Add PCD to enable runtime serial debug >> ArmVirtPkg: add runtime instance of FdtPL011SerialPortLib >> ArmVirtQemu: enable runtime debug by build flag >> > > Hello Heyi, > > We have had this discussion before, and IIRC, the proposed solution > was to use status codes. > > I'm not sure how that is supposed to work though - hopefully Laszlo or > one of the MdeModulePkg maintainers can elaborate. Here's the basic idea. Status Code reporting and routing are defined by the PI spec for OS runtime as well, not just boot time. Recently we added status code *routing* to ArmVirtPkg, in commit 5c574b222ec2, via the generic runtime driver "ReportStatusCodeRouterRuntimeDxe". We also added the library resolution ReportStatusCodeLib --> MdeModulePkg/Library/DxeReportStatusCodeLib/DxeReportStatusCodeLib.inf (for some module types). As a result, when modules of those types report status codes, they now reach the ReportStatusCodeRouterRuntimeDxe driver, which "routes" the status codes. In the same series, we also modified ArmVirtPkg's PlatformBootManagerLib (built into BdsDxe) to register a status code *handler* callback with ReportStatusCodeRouterRuntimeDxe -- but only for boot time (not runtime), and only for a very specific group of status codes. As a result, when a module of suitable type reports a status code, ReportStatusCodeRouterRuntimeDxe "routes it" to BdsDxe, and then BdsDxe "handles it" (in our implementation, we simply format it to the UEFI console), assuming the status code is the kind we are interested in. Now we come to the current series. First, the series adds the following DebugLib class resolution: DebugLib --> MdeModulePkg/Library/PeiDxeDebugLibReportStatusCode/PeiDxeDebugLibReportStatusCode.inf This will cause modules to publish their DEBUG messages as status codes via ReportStatusCodeLib, rather than log them via SerialPortLib. (I'm too lazy to check the exact status code classes etc that PeiDxeDebugLibReportStatusCode embeds the DEBUG messages into.) As a result, DEBUG messages will reach ReportStatusCodeRouterRuntimeDxe for "routing". As another result, until we reach a late enough stage in the boot, those messages will not be printed by anything (because there's not going to be any "handling" for them). (The present series also updates the ReportStatusCodeLib resolution so it can be used at runtime too, but that's quite auxiliary to this discussion.) Second, this series includes the generic Status Code *handling* driver (also a runtime driver): "StatusCodeHandlerRuntimeDxe". Independently of the particular handling that we already have in BdsDxe via the earlier series, this generic status handler driver registers a handler callback that simply prints status codes to the serial port (dependent on a PCD setting), via SerialPortLib. With the modification from the first patch, this generic status code *handler* driver is extended to runtime serial port operation. And, the second patch in the series provides a SerialPortLib instance for it that can work at runtime. All in all, when a runtime driver calls DEBUG, this happens: runtime driver calls DEBUG -> PeiDxeDebugLibReportStatusCode -> RuntimeDxeReportStatusCodeLib [status code reporting] => ReportStatusCodeRouterRuntimeDxe [status code routing] => StatusCodeHandlerRuntimeDxe [status code handling, such as SerialPortWrite():] -> FdtPL011SerialPortLibRuntime This is actually a good idea, but it would be nice if: - QEMU had two PL011 ports, - the boot time firmware log, and the OS log, went to one port - the runtme firmware log went to the other port. Given that this series provides the SerialPortLib instance for StatusCodeHandlerRuntimeDxe anyway, we could implement it so that it locate a "special" PL011 in QEMU's DTB -- the port that we'd only use for runtime firmware logging. I don't insist that this series implement all of that, but it should either prevent a conflict on the one PL011 between the firmware and the OS, or else be very explicit about the possible conflict in the commit messages. Thanks Laszlo