Date: Mon, 8 Sep 2008 22:34:23 +0200 From: Juergen Lock <nox@jelal.kn-bremen.de> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-emulation@freebsd.org, peter@freebsd.org Subject: Re: Linux applications core if running (k)qemu Message-ID: <20080908203423.GA12147@saturn.kn-bremen.de> In-Reply-To: <20080907215300.GH2038@deviant.kiev.zoral.com.ua> References: <alpine.BSF.1.10.0808291711580.5866@thor.farley.org> <20080830113448.GA2152@dchagin.dialup.corbina.ru> <alpine.BSF.2.00.0809021552040.7934@thor.farley.org> <20080906104659.GA2113@dchagin.dialup.corbina.ru> <200809062215.m86MF6NS040797@saturn.kn-bremen.de> <20080907215300.GH2038@deviant.kiev.zoral.com.ua>
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On Mon, Sep 08, 2008 at 12:53:00AM +0300, Kostik Belousov wrote: > On Sun, Sep 07, 2008 at 12:15:06AM +0200, Juergen Lock wrote: > > In article <20080906152929.GB2038@deviant.kiev.zoral.com.ua> you write: > > >-=-=-=-=-=- > > > > > >On Sat, Sep 06, 2008 at 02:46:59PM +0400, Chagin Dmitry wrote: > > >> On Tue, Sep 02, 2008 at 03:56:33PM -0500, Sean C. Farley wrote: > > >> > On Sat, 30 Aug 2008, Chagin Dmitry wrote: > > >> > > > >> > >On Fri, Aug 29, 2008 at 05:29:09PM -0500, Sean C. Farley wrote: > > >> > >>I am having trouble with kqemu.ko and linux.ko. If I run qemu with > > >> > >>the following command, Linux applications (chroot, acroread, ls) will > > >> > >>start core dumping: > > >> > >> qemu-system-x86_64 -m 512 \ > > >> > >> -drive file=/usr/QEMU/WinXP/c.img,if=ide,media=disk -boot c \ > > >> > >> -std-vga -parallel none -serial none -monitor stdio \ > > >> > >> -net nic,model=e1000 -net tap,ifname=tap0,script=no -localtime > > >> > >> > > >> > >>Loading kqemu.ko does not cause the problem, but the cores start a > > >> > >>little after WinXP starts running. Unloading kqemu.ko does not help; > > >> > >>the cores still happen but more randomly. I even tried unloading all > > >> > >>linux modules and reloading them without luck. It takes a reboot. > > >> > >> > > >> > >>Packages: > > >> > >>qemu-devel-0.9.1s.20080620_1 > > >> > >>kqemu-kmod-devel-1.4.0.p1 > > >> > >>linux_base-f8-8_4 > > >> > >> > > >> > >>sysctl: > > >> > >>compat.linux.osrelease: 2.6.16 > > >> > >> > > >> > >>dmesg: > > >> > >>kqemu version 0x00010400 > > >> > >>kqemu: KQEMU installed, max_locked_mem=1792492kB. > > >> > >> > > >> > >>System is 7-STABLE as of r181963 with or without the patch to fix RT > > >> > >>signals from Chagin. > > >> > > > > >> > >Interestingly... Sean, can you provide ktrace/kdump log of coring > > >> > >apps? thnx! > > >> > > > >> > Here they are (good and bad): > > >> > http://www.farley.org/freebsd/tmp/linuxulator_vs_kqemu/ > > >> > > > >> > The good trace is after the bad trace. I just kept running ktrace > > >> > /compat/linux/bin/date over and over until I got a good trace. Before > > >> > loading kqemu and running qemu, there were no core dumps. Also, I > > >> > compared two bad traces and they were basically the same except for PID > > >> > and a couple of addresses (still very close in value). > > >> > > > >> > > >> Most likely it is a tls problem again, some days ago kib@ has made MFC > > >> r182684, probably it will help.. > > > > > >I doubt it. This seems to be an ingenious kqemu bug. As far as I remember, > > >it tries to use GDT/LDT. This probably has unwanted interaction with > > >PCB_GS32BIT. > > > > Wow. That corner of the code had escaped me so far, and yes this (in > > amd64/linux32) looks like it won't like kqemu's seperating of the gdts > > on SMP indeed. (it stores a pointer to &gdt[GUGS32_SEL] in pcb_gs32p and > > lets linux processes manipulate the segment pointed to by it, and when > > kqemu is (or was) running this won't be used by all cpus, see older threads > > like > > http://lists.freebsd.org/pipermail/freebsd-emulation/2008-May/004902.html > > for the reasons.) > > > > What I wonder tho is, won't this also cause problems without kqemu when > > there are linux processes running on multiple cpus that manipulate this > > segment because the gdt is then shared between the cpus? (like, linux > > process on cpu 0 changes the segment, then linux process on cpu 1 comes > > along and changes it again and then the linux process on cpu 0 will pick > > it up from cpu 1?) At least I must have somehow assumed the shared gdt > > wouldn't be changed later because of reasons like this... > > Very nice catch! Me and Peter Wemm discussed the right approach, > that consists of actually providing per-cpu GDT. Patch is at > http://people.freebsd.org/~kib/misc/amd64_gdt.1.patch > > Please, test and give a feedback. Even reports about thinks working > the same as before the patch are important. OK I just tested the patch on RELENG_7 (updated my amd64 SMP box from RELENG_7_0) and found no problems. (I tested linux date(1), googleearth, kqemu, and a few other non-linux things so far.) Thanx, Juergen
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