From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH] lguest32 kallsyms backtrace of guest. Date: Thu, 05 Apr 2007 12:54:12 +1000 Message-ID: <1175741652.12230.620.camel@localhost.localdomain> References: <1175711023.9371.21.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <1175711023.9371.21.camel@localhost.localdomain> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Steven Rostedt Cc: virtualization@lists.osdl.org, Linux Kernel Mailing List List-Id: virtualization@lists.linuxfoundation.org On Wed, 2007-04-04 at 14:23 -0400, Steven Rostedt wrote: > This is taken from the work I did on lguest64. > = > When killing a guest, we read the guest stack to do a nice back trace of > the guest and send it via printk to the host. > = > So instead of just getting an error message from the lguest launcher of: > = > lguest: bad read address 537012178 len 1 > = > I also get in my dmesg: > = > called from [] show_trace_log_lvl+0x1a/0x2f Hi Steven, This is a cool idea, but there are two issues with this patch. The first is that it's 500 lines of code: that's around +10% on lguest's total code size! The second is that it conflicts with the medium-term plan to allow any user to run up lguests: this is why lg.ko never printk()s about problems with the guest. While it is useful for cases where a guest dies mysteriously before it brings up the console, three alternatives come to mind: 1) Modify early_printk so Guests can use it. 2) Have a separate tool(-set?) for this kind of post-mortem. Then you just have to implement guest suspend! 8) 3) Put this in a CONFIG_LGUEST_DEBUG. Note that options 1 or 2 make you do more work, but are probably better in the long term. I'm happy for #3 to sit as a patch in the tree for the duration, tho! Cheers, Rusty.