From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MR1v6-0005Hb-6y for qemu-devel@nongnu.org; Wed, 15 Jul 2009 06:41:04 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MR1v1-0005EW-5S for qemu-devel@nongnu.org; Wed, 15 Jul 2009 06:41:03 -0400 Received: from [199.232.76.173] (port=49755 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MR1v0-0005EI-J2 for qemu-devel@nongnu.org; Wed, 15 Jul 2009 06:40:58 -0400 Received: from lizzard.sbs.de ([194.138.37.39]:19054) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1MR1uz-00087b-M5 for qemu-devel@nongnu.org; Wed, 15 Jul 2009 06:40:58 -0400 Message-ID: <4A5DB231.7040109@siemens.com> Date: Wed, 15 Jul 2009 12:40:49 +0200 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] monitor: Add port write command References: <4A5C3FBB.10306@siemens.com> <200907142030.27019.paul@codesourcery.com> <20090715073451.GF28046@redhat.com> <200907151114.21482.paul@codesourcery.com> In-Reply-To: <200907151114.21482.paul@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: Anthony Liguori , qemu-devel@nongnu.org, Gleb Natapov Paul Brook wrote: >>> I'd be reluctant to expose the savevm state to the user. >>> >>> For debugging qemu I don't see it providing any real benefit over firing >>> up GDB and poking directly at the device directly. >> Not all environments where you need to debug things have gdb, qemu >> sources or even non striped qemu binary. > > If you don't have qemu sources than I really don't care. By definition you're > not going to be able to do anything useful even if you do figure out what the > problem is. Note that there's no requirement that you run gdb on the target > itself. Remote debug (e.g. via gdbserver on linux) is a well established > technique. > > Likewise for debugging stripped production binaries, my answer is "don't do > that". There are very rare cases where a bug goes away on a debug build, but > in those cases any instrumentation you add is also liable to make the bug go > away. Again, having to debug qemu itself when all you want is some additional information about the emulated hardware state while debugging a guest seems like overkill to me. Imagine you are attached to qemu's gdbstub and stopped the guest that has some issue using, say, the apic. And now imagine you could simply issue e.g. (gdb) monitor devstate apic.1 apicbase=... tpr=... icr={..., ... } lvt={..., ... } ... That would provide you a nice picture of the virtual hardware state without the need to fire up and operate a second gdb just to obtain this data. And manipulating some lvt register would only be a trivial additional monitor command away. Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux