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Date:      Thu, 10 Sep 2009 14:28:50 +0300
From:      Kostik Belousov <kostikbel@gmail.com>
To:        Vincent Hoffman <vince@unsane.co.uk>
Cc:        freebsd-stable@freebsd.org, John Baldwin <jhb@freebsd.org>
Subject:   Re: general protection fault on boot.
Message-ID:  <20090910112850.GG47688@deviant.kiev.zoral.com.ua>
In-Reply-To: <4AA8D62F.1020901@unsane.co.uk>
References:  <4AA7D8B3.1010203@unsane.co.uk> <200909091339.00193.jhb@freebsd.org> <20090909190228.GC47688@deviant.kiev.zoral.com.ua> <4AA8D62F.1020901@unsane.co.uk>

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On Thu, Sep 10, 2009 at 11:34:23AM +0100, Vincent Hoffman wrote:
> Kostik Belousov wrote:
> > On Wed, Sep 09, 2009 at 01:38:59PM -0400, John Baldwin wrote:
> >  =20
> >> On Wednesday 09 September 2009 12:32:51 pm Vincent Hoffman wrote:
> >>    =20
> >>> Hi all,
> >>>           I've been running the 8.0-BETAs in a xen virtual machine
> >>> (hvm/fully virtualised) for testing and something between r196730 and
> >>> r196746 causes a general protection fault on boot. I'll try and narrow
> >>> it down if i get a chance but I'm a a bit busy at the moment.
> >>> =20
> >>> backtrace is available at
> >>> http://unsane.co.uk/~jhary/freebsd/GPF-09-09-09.gif=20
> >>> Xen dom0 is a centos5.3 box using the xen-3.3.1 rpms from
> >>> http://www.gitco.de/linux/i386/centos/5/rpms/  if thats of any use.
> >>>
> >>> Let me know if I need to provide any more info.
> >>>      =20
> >> Hmm, can you try reverting 196737?  Or actually, can you print out the=
 value=20
> >> of %ebx ('p $ebx' in ddb will work I think)?  I wonder if this patch w=
ould=20
> >> fix it:
> >>
> >> Index: pmap.c
> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >> --- pmap.c	(revision 196974)
> >> +++ pmap.c	(working copy)
> >> @@ -999,7 +999,7 @@
> >>  		 * coherence domain.
> >>  		 */
> >>  		mfence();
> >> -		for (; sva < eva; sva +=3D cpu_clflush_line_size)
> >> +		for (; sva <=3D eva; sva +=3D cpu_clflush_line_size)
> >>  			clflush(sva);
> >>  		mfence();
> >>  	} else {
> >>    =20
> >
> > Oh, no, another pointy hat to me :(.
> >
> > Please, try this patch instead.
> >
> > diff --git a/sys/i386/xen/pmap.c b/sys/i386/xen/pmap.c
> > index 4b81aae..122318c 100644
> > --- a/sys/i386/xen/pmap.c
> > +++ b/sys/i386/xen/pmap.c
> > @@ -1004,8 +1004,8 @@ pmap_invalidate_cache_range(vm_offset_t sva, vm_o=
ffset_t eva)
> >  		 * coherence domain.
> >  		 */
> >  		mfence();
> > -		for (; eva < sva; eva +=3D cpu_clflush_line_size)
> > -			clflush(eva);
> > +		for (; sva < eva; sva +=3D cpu_clflush_line_size)
> > +			clflush(sva);
> >  		mfence();
> >  	} else {
> > =20
> >  =20
> Hi,
>     I tried this this morning with no joy i'm afraid.
> not much change but new backtrace (with p $ebx) at
> http://www.unsane.co.uk/~jhary/freebsd/10-09-09.gif
I would need the panic message and ddb lines that are not
present on your screenshot.

Also, the dmesg is interesting (CPU features report).
>=20
> Just to check I'm not in need of more coffee as i'm still learning svn
> (and my coding skills such as they are lie in shell and perl)
>=20
> krill# svn info
> Path: .
> URL: svn://svn.freebsd.org/base/stable/8
> Repository Root: svn://svn.freebsd.org/base
> Repository UUID: ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
> Revision: 196740
> Node Kind: directory
> Schedule: normal
> Last Changed Author: rnoland
> Last Changed Rev: 196737
> Last Changed Date: 2009-09-01 17:41:28 +0100 (Tue, 01 Sep 2009)
>=20
>=20
> krill# sed -n '1010,1017p' sys/i386/xen/pmap.c
>                  * coherence domain.
>                  */
>                 mfence();
>                 for (; sva < eva; sva +=3D cpu_clflush_line_size)
>                         clflush(sva);
>                 mfence();
>         } else {
>=20
> krill#
>=20
> Happy to give vnc access to the console of the machine if that would help.
>=20
> Vince

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